Agreed, I think "proper" delivery drivers are slightly different as they are paid per hour of work and its a "proper" job as such, where as mine is to make extra and my only way of making money at that job is on delivery and tips, some are better than others, i don't expect a tip but some people dont even say hi or thanks and to me thats just rude
You should get paid an hourly rate that definitively takes you to minimum wage.
FWIW, other than that, several food delivery drivers are not quite so different to what you seem to think. They don't all do it as a 'proper' job as you call it, they have other jobs and do it to make extra money (or favours). The days of full time contracts in 'daytime hours' where you got paid a lot more than minimum wage are long, long gone. Not that I think many people who've done deliveries for a living and know a heck of a lot more than I do would necessarily stress this, I'm sure they'd talk of the casual nature of jobs going back decades and have a laugh at all of us.
Your job has differences, but the very clear demarcation you are making between your job and some others is I would say much,much more blurred than you are making out.
As for tips, people can infer things from what I've written if they wish.