Why are people given such limited time to make food/drink-related decisions?

When I walk into a order-at-the-counter food place, I need a few minutes to decide what I would like to order. I usually stand back, away from the counter, looking up at the menu while I make my decision. But the cashier always asks, immediately upon walking in (if there are no other customers), “Can I help you?” Like, clearly, I only walked in a second ago and am currently looking at the menu.

I run into a similar problem at some sit-down restaurants because the server will frequently ask what we want to drink the moment we are seated! I’ve been so caught off guard by this in the past that I’ve just asked what was on tap because I felt so pressured to make my drink decision at that moment. But then after ordering my beer and having a moment to actually look at the drink menu, I realize that there is a drink special I’d much rather have had than the beer I hastily ordered. I don’t understand why servers would ask people what they want to drink before they have even had a chance to look at the drink menu! Don’t they want people to order the $10 martinis from the drink menu? If the server doesn’t even give you a chance to check out the martini selection, how do they expect to be tipped on it?