Point being? That's their job, and they're not doing any of that exceptionally...and you as a customer don't even know if you've got the right order when you're forced to make a decision to tip.
Your argument is like this. A lifeguard at the YMCA opens the pool, cleans the deck, puts in the lanes, takes them out during family times, answers questions about the facility, and oh yeah...protects and saves people. Why don't you tip the lifeguard? It's their job, and you expect all of those things to be taken care of.
When I order a pizza, I expect the order to be taken, cooked in clean pans (health regulations?), and delivered. I don't expect the delivery boy to wait around at my place, make sure I like the pizza, and exchange it if I don't. I don't expect him to drive like an idiot and get into an accident (there are hazards at ANY job), etc. Come up with a valid argument that doesn't say "he does his job, he needs a pat on the back," and I'll listen.
P.S. around here delivery drivers get ~$3 over minimum wage, gas paid for...umm, yeah, sorry, there are jobs that require a lot more work and don't get paid that. No tip man, they don't do a damn thing better than they're expected to to keep their job.