Why would anyone want 180g records ?

DJs like the 180g records; they're heavier, and have a better feel for spinning and scratching.

In the original days of vinyl (aka records or LPs), audiophile recordings were pressed on 180g virgin vinyl rather than the common 120 to 140 gram. It's my understanding that creating a thicker record with deeper grooves could hold more information.

Nowadays, identifying a record as "180 gram" is a marketing term; if it's thicker, it must sound better.
A good sounding vinyl pressing comes from good mastering, an expert record cutter and technicians, and well maintained equipment. The actual vinyl disk could be 120g and have excellent sound.

Of course, some of today's pressings do have excellent SQ, my point is that it's not due to the vinyl being 180 or 200g. But that's what they've given us.
As far as advantages, one of the selling points is less likely to warp, even though some new records are leaving the record plants warped.

Raul, that's a great point about record prices going up, not down.

I think record prices will remain high due to record pressing plants having to maintain and upgrade equipment that has been put back into service, plus there are a number of new record plants with start-up costs.

There may also be a greed factor; record labels and vendors wanting to make quick money while the vinyl business is hot.
A typical price for a 180g LP at SS Direct, Music Direct and others used to be $24.99, now new releases are higher.