Clark doesn’t have the speed to avoid detection and identification…

Why steal a disguise if you can “streak” like an invisible blur?

…until after gaining flight (and even then).

Granted, when we approach a film based on a preexisting property, as an audience we bring the baggage of expectation, but it is unfair to criticize the character’s in-film choices for abilities that haven’t been established. The film gives us a clear precedent for Clark developing his powers later than he is potentially capable of and later than tradition with flight.

Consider the following sequences which go differently if Clark has enough speed to avoid detection and identification:

• Maybe – Jonathan’s puts a premium on Clark being deliberate about his secret because unlike most previous versions of Superman, Clark can’t simply become invisibly fast (a red blue blur if you will) or take off, straight up into the sky, to avoid identification or the consequences of using his powers publicly.
• Tornado – Clark CAN’T rescue Jonathan without revealing his secret. Jonathan knows this and so he forestalls Clark from letting the world know he exists for now. Note too that afterwards, they’re all stranded in the middle of nowhere (the highway backed up for miles) with the witnesses. Implicitly, Clark can’t just zip them all to the Kent farm to remain anonymous afterwards.
• Oil Rig – Here, Clark clearly wants to save these people. They already know he has powers when they see him tear a door off its hinges and standing there in flames. Time is of the essence and there is a premium on speed. Clark has already heard the Coast Guard say over the radio, “Forget them. They’re dead.” He needs them topside ASAP, not just to avoid the danger, but to be rescued by the Coast Guard who have nearly given up. However, we see Clark leading them simply moving at normal speed and waving them on. He doesn’t carry them one or two at a time using super speed, likely because he can’t.
• Clothing – After the oil rig rescue, Clark comes ashore shirtless, shoeless, and his pants in tatters. His secret is still important, so he needs a disguise to maintain the appearance of normalcy (something not maintained by asking for the clothing). So Clark steals. It isn’t out of physical necessity but to preserve his secret. However, if Clark could fly or move at speeds rendering him undetectable or unidentifiable, then he wouldn’t have to steal these clothes, would he? That might give new meaning to the word “streak” but he wouldn’t need clothes to hide if he had speed to “hide” with (or get him to clothes obtained without moral compromise).
• Hitchhiking to Ellsemere – Clark gets a lead on something interesting and makes his way there. However, as Lois writes later, “A background check revealed that his work history and identity had been falsified.” Clearly, Clark does not want to leave behind evidence of his comings and goings. What better way to do that than to run to Ellsemere undetected if you could? Unless you couldn’t.
• Ellsemere Job – If Clark can move invisibly fast and manipulate objects at speed without destroying them on impact, why even bother to get a job at Ellsemere as baggage handler “Joe” at all? He can simply zip throughout the camp and grab whatever intelligence he so desires. That aside, once you’re there, why would you approach the Scout Ship at normal speed for Lois to spot you and wonder, “Where the hell are you going?” unless moving normal speed is more discrete than moving at what you know to be your upper limit is?

I’m NOT saying that at these points in the film Clark can’t muscle more speed out to move faster than anyone else.

I’m highlighting the HUGE gap between using strength to mechanically move faster and supernaturally moving faster than visual detection and identification… and an even further gap to be allowed to supernaturally and harmlessly interact with objects at that speed (not killing Jonathan or the Oil Rig Workers moving at such speeds, being able to extract information from computers, not having normal clothing disintegrate under such speed, etc).

Faora appears to be the only possible counter example, but she is distinguishable from Clark in many regards. It took Clark 33 years to tap into flight, but it took Zod less than a day. What Faora may be able to do in a short amount of time does not dictate how long it may take Clark to arrive at the same. Faora moves almost invisibly fast, but is still detectable and doesn’t perform her strikes while still moving invisibly fast. She’s only invisible-ish for short, straight, staccato bursts with no indication that the individuals on the receiving end of her speed would be protected from it… that is, this speed appears useless for carry-style rescue or invisibly stealing data from computers. Faora is also wearing the durable Kryptonian armor, so there’s no indication that normal clothing could survive her speed. Lastly, we don’t know the depth or degree of Faora’s training when compared to Clark, who was essentially raised never to use his powers in anger.

The next time someone raises what Clark “should” have done with his super speed, you can ask whether their assumption of that speed is justified by anything in the film.