A lot restict tethering on mobile sims though, which is why the 3 mifi is a good deal. Although somewhat expensive it’s a good alternative.
It’s to stop people using thier phones as hot-spots in lieu of proper broadband and saturating the 4g bandwidth with video streaming, torrents and news groups, the network can’t cope.
If you start using 200gb a month on a 4g mobile, they’ll soon throttle your connection.
A lot of people were doing that, and constantly downloading torrent and other bandwidth intensive activities on 4g, and it was spoiling connectivity for normal users.
The mifi is specifically aimed as a broadband substitute, but it’s limit in terms of total downloads per month for the same reasons. It doesn’t have the same restrictions on the account, but you are capped at 30-50gb a month total.