A really nice waitress at restaurant I've been going once or twice a week for lunch for the past several months quit this week, kind of makes me sad. If tipping is being polite, then I don't understand why you wouldn't do it when someone gives you tasty food and is friendly.
Upselling can put people off.
If they wanted it they would have ordered it. Sure highlighting a deal or an offer is one thing because it could benefit the customer. If the upselling doesn't benefit the customer it should be avoided.
Not the fault of the person offering it though. They are at least as annoyed at having to do that as the customer is for being asked about it.