Could it be he wanted to spend a night in town hitting the bars? Could it be that it's none of your, or the cop's, business?
Dropping $60 on a cab trip into town for a night of hitting the downtown bars with buddies wasn't all that uncommon of a thing back in college. And none of us were "wealthy" then by any means. That didn't automatically make us "drug dealers" or whatever else it is you are libelously attempting to claim about this kid.
See red above.
If the reason is unknown to you, then why do you keep bringing it up with the not so subtle and completely libelous implication that he was in Seattle for a drug deal?