At almost every birthday bash, anniversary party, awards ceremony and even engagement party I often find the master of ceremonies speaking dismissively of formalities. "We will soon be done with the formalities and dinner will be served" or "With the formalities over let's enjoy the rest of the evening with drinks at the bar to my right and a DJ to keep us dancing 'til the morning!"
In this culture of haste and short attention spans a disturbing number of guests just want to get to the eating, drinking and dancing: forgetting that these are periphery aspects of the function. MC's for the most part are on the same boat and the whole event feels like everybody is waiting for the priest to finish his sermon, the birthday boy to cut his cake and blow the candles, or for the emotional sister to get her speech over and done with quickly. It's a testament to the general de-sensitization and decreasing levels of patience in people that they can't sit still, be quiet and observe.
These days the so-called formalities are treated as a necessary evil, much like paperwork or cleaning the house - people want it to be done with as quickly and painlessly as possible. They don't observe the formalities, they merely tolerate it.
You are not entitled to eat and get drunk
At any event there is no obligation to provide guests with food, drink and entertainment; doing so is just good practice in honouring your guests. To be invited to somebody's anniversary/birthday/graduation party means that you're someone reasonably dear to the host (caterers charge per head). You are there to witness and share in something important to the host; eating and getting drunk is a secondary perk. The so-called formalities are the very reason you attend a function in the first place and you need to be cognizant of that even if it goes 30 minutes longer than expected.
Next time before responding to the RSVP request, ask yourself whether you would attend if there was no food, entertainment or alcohol. If your answer is no, cede your invitation to someone that sees formalities as more than an obligatory inconvenience.