At some point Walter and Jesse have to come in laundry trucks leaving their cars away. I understand Hank may watch Walter, but why Jesse?
It's not a case of Hank possibly watching Walt, it's more that the launderette was on his radar and known to him as a potential target. If he'd been watching it over any space of time, he'd start to notice who goes there regularly.
If that person was someone he knew to have links to drugs, and also was a completely different race from the other employees there, then that's going to set further alarm bells of in Hank's head and confirm his suspicions that something illicit is going on (rightly or wrongly).
By having Walt and Jesse come in the back of a laundry truck, it looks like a regular drop off and doesn't raise any flags with anyone.
It is a plot hole.
If the lab is secret , then Walt could certainly drive to it as often as he liked provided that he had ensured he wasn't followed and he took different routes to and from it. The same would go for Jesse Pinkman, although he would had to been more circumspect as he al;ready had a police record and that could have been used to call attention to him as a suspect.
Taking them to and from the lab would have been a sensible plan from teh beginning. It would limited any visible connection between the two and the lab. And it would have made it easier to spot any potential tails as the pickup and dropoff sites could be placed under surveillance prior to their use. This very obvious piece of tradecraft seems to have escaped the writers.
In any case, Hank was originally suspicious of Jess Pinkman so if any one was going to be followed it would have Pinkman first and then Walter White , if or when any suspicion fell upon him as being involved in drug activity. It would have made sense to transport at least Jess from the very beginning and then later Walt as circumstances changed.