Because having the option of using a micro SD can provide additional storage that is significantly less expensive than buying a phone with larger storage capacity.

Pics of yo momma.

I've about 2,000 and counting FLAC files on my micro SD card for high quality audio. Many from my CD collection, and a nice amount obtained through other means. I'm already at 90 gigs used in my 256 gig card.

I'll be getting a new phone at the end of the year, and to transfer all that music (plus my commissioned art collection) all I'd have to do it just pop the card into the new phone.

No wrestling with cloud storage subscriptions or having to worry about my digital stuff being in somebody else's hands. Just keep it on a tiny card smaller than my fingernail and back it up periodically to my desktop and my laptop. Best part is that I don't even need any adapters to use headphones, as Motorola phones still have headphone jacks.

There's people with downloaded movies and shows they like having local access to without any streaming woes, folks who take tons of photos and videos, etc. Having an SD card slot is one of the requirements I need for me to want to use a phone.

"If I dont have a problem that means NOBODY will EVER have that problem"

Are you dumb? If you don't want that many storage space doesn't mean others don't want it?