It's certainly not popular in the UK. It's just too expensive. It costs ~ £0.50 per mms to send so people will just use email / facebook / whatsapp / whatever.

MMS as in telecom operator carried multimedia messages?

I thought phones didn't even support this anymore. I've never seen anybody using it, and I wouldn't know how to send one.

All the multimedia messages I see people using are transmitted through the Internet.

Open text messaging app on android -> attach image -> hit send

There, it sent an MMS. It's transparent to the user.

Non-MMS: Hangouts to another Google user, Whatsapp, Telegram, Viber, etc etc

In my experience in the US, it's still the primary way of sending graphics/pictures via phone.

It really boils down to if people pay or not.

In the US most people are still on a monthly plan that includes "unlimited texts" (inc. MMS). In many other places a single MMS can cost you between 5c-$1, so people use WhatsApp, Google+, or many other free (or cheaper) alternatives.

But MMS is definitely popular in certain regions. It is also very unpopular in regions. If you're in the UK you could very easily disable MMS, but in the US? I wouldn't...

Yep, didn't point that. My experience is at Brazil.

Perhaps in USA is popular, in Spain and Italy it is not very popular because it is expensive and other messaging solutions are used, like Whatsapp