this, so they will have to cut little to no weight, without the risk of being weak/dehydrated from a big weight cut which usually makes fights slow and boring

The actual event itself starts at 5 pm. Getting the weigh in stage and all that changed too and from that quickly would be extra money for the organization if it's even possible. Not to mention all the overtime everyone would get paid.
If they do it the day before they have another day to gain publicity and extra revenue. It's more of a financial decision.
Besides, EVERYONE except like Frankie Edgar cuts weight now a days.

people should stop getting so caught up on weight, if a fighter is good 20lbs doesn't matter

Revenue over integrity.

its not a charity bud, if you don't like the way they do their business then you have the option to not watch/buy anything with a UFC logo on it, otherwise you gotta accept that it is a business and profits must be a top priority for it to survive.

20 lbs @ heavy weight isn't as big a deal as 20 lbs at lightweight.

yeah, but Frankie Edgar and Jens Pulver cut little to no weight when they fought at lightweight and both held the gold at one point, all i'm saying is size isn't everything

of course not, the whole division can be anywhere from 30pounds difference... in HW..

anyways there's still a few guys who can be able to do that easily. Frankie could pull it off, and because this day in advance weigh in it's the only reason he lost the belt. it is possible to be good and fair.

I think fair would be weighing in as you step into the ring.