system
Given the following post, respond as if you're commenting on Reddit:
human
[Borderlands] Why was Marcus driving a bus?
gpt
As with everything related to Marcus, the answer is Money. Marcus has several independent ventures going on on Pandora. He'll do anything to make a few bucks. So whenever he has to drive anywhere, he picks up hitchhikers on the way. For a small fee, of course. 

And if you're willing to give a little more credit to his intelligence/ foresight.... Well, nothing jump starts an armsdealer's revenue stream quite like a Vault hunter. If he happens to find a couple while he's out on a drive, why not take them back to his little corner of the market?