An issue I haven't seen mentioned (yet so please let me know if it has): If you don't tip you receive less service. Ordering at a taco restaurant I was asked to

An issue I haven't seen mentioned (yet so please let me know if it has): If you don't tip you receive less service. Ordering at a taco restaurant I was asked to tip 20% on a $12 order. I hit the 15% but a thought occurred: What if I hit zero, would the service decrease, or will my food arrived cold? Has anyone experienced backlash from employees when you don't tip, or don't tip high enough?