WHY punish good customers?

I am a home owner, but I don't own a 'home tower' (SoCal Edison owns it - and leases space to T-Mobile).  I do also have 'T-Mobile Home Internet', and it works quite well.

Typically it wouldn’t help me much to take it with me where I travel, as T-Mobile has a hotspot service (included),  and the device is a little bulky.

If I were to be using an RV or living on the road/streets, and needed to use a laptop/tablet/etc. I’d upgrade as @gramps28 states, or use a portable hotspot - and activate as needed.

Not all 'towers' are built the same and have the same amount of backhaul capacity, but many can/have used many hundreds of GB (+1 TB even) for 'typical' monthly use.  Personally, I might think that the cost is prohibitive (i.e. why don't they make a 'summer' plan much like allowing temporary unlock on a device) - $100 for 1 month national use ?  I suspect that this is more of a lockdown.  I 'could' rent a 2nd device to go to a cabin in the woods during the summer for a month.

You must not own a home tower. People who own them have been using them as they travel, but the message from T-Mobile id that they are shutting them down if the move them.

I think that you need to clarify.  I don't see any punishment for connecting to mobiles towers.