I bet UFC would love to be able to stack every card with mostly fighters in the same weight class.
So, if one of the main eventers failed to make it to the fight, there is a larger selection of fighters who can be a replacement.
Unfortunately, it's difficult enough to even get fighters to take a match.
Imagine Khabib Vs Connor happens. There are so many things that could go wrong with all the shenanigans going on.
Perfect scenario is to put on the same card: -
Poirier Vs Alvarez
Gaetjhe Vs Iaquinta
James Vick Vs Paul Felder
Kevin Lee Vs Alexander Hernandez
Barboza Vs Chiesa
So, someone like Connor snorts himself into jail again. Loads of guys on the card would love to challenge Khabib (especially Kevin Lee).