I'm amazed that people actually use their cellular data, even when they have routers.
I use Wi-Fi 99% of the time so this plan works out for me.
same for me. I even disable data usually and just use wifi. The only thing I noticed that data is required for at least on android is picture messaging. It doesnt work with wifi. On average I use only about 0.1 gb a month. So the option to pay almost nothing for data plan does sound very nice.
Plenty of people don't have very reliable wifi service. For me, my internet suffers from slowdowns, random shutdowns, etc. After awhile, it just gets easier to use mobile data. Besides that, if you actively travel almost anywhere, odds are your data will be far faster than whatever wifi you may be able to leech off of for one block at a time. I mean, as someone that travels for hours on public transport when I go anywhere outside of about a 30 block radius of my home, a good mobile data plan is beautiful. With unlimited data, that means if I'm on a bus for an hour, I can easily just load up some Netflix without worry. It doesn't require preparation by downloading a show in advance at home, and it's quick and simple.
All in all, there are a lot of benefits to mobile data. Hell, even if I'm just on my college campus, the internet often cuts out when too far between buildings, and some buildings just don't have wifi that reaches more than a few inches beyond the walls of the building in question. That means if I'm going somewhere on campus and want to check my phone for social media or whatever, the easiest way to do it is via mobile data.
Hell, with unlimited data, I could make a reliable wireless hot spot if I wanted to making it so my laptop could effectively be used fully anywhere I go that I get a cell signal.
Honestly, it sounds like you two just don't go much of anywhere, or only travel between two locations with a short commute where having data is a kind of a non-issue. That's not a bad thing, but it really isn't that hard to see how people can go through quite a bit of data.