Not everyone buys Samsung, there are a lot of cheap SSD's out there that are rated for only a handful of TB's a year.
There is also a case of the silly SSHD's or w/e which combine a tiny SSD and a mechanical component which can die considerably faster.
Overall the amount of writes an SSD can handle is tied directly to it's capacity since it determines the amount of average writes per a given time unit that each cell will experience as long as the firmware actually does it's job (in Samsung's case it may very well not do it as they had more than a few firmware screw ups in the past).
This can also more severely affect you if you have a medium sized drive (say 128-256GB) but it's pretty full.
A good SSD's will move things around somewhat to even out the wear but it still increases the amount of writes you have.
If your SSD does have an "even wear" feature when you write 12GB to drive which is say 50% or more full it usually triggers more than 12GB of effective writes in the drive itself as the firmware would move already written data around to ensure that every cell has been written to approximately the same amount (if you say only have 20GB of free space and you write 12GB daily and delete it, your effective writes would be closer to the full capacity of the drive per day than to 12GB).
You also have a lot of embedded/mobile devices which use considerably shittier storage than modern SSD's, you can easily chew through a SD card or a similarly rated flash storage with anywhere between a few 100's of gigs to only a handful of TB's (or a only few times the capacity of the card if buy bargain bin memory cards).
Since these machines are more commonly used these days it's not a feature that should be so quickly obfuscated from the user since it doesn't seem like there is an "intelligence" behind how conservative or not the browser is with writes to local storage.
If you install firefox on an SBC/netbook/microcomputer or even a mobile phone (if this affects the mobile version also) with eMMC/MMC only rated storage 12 gigs a day can and will kill it rather quickly.