The part you're missing is (ignoring story consequences).
(ignoring story consequences).
I've played with a party who were really amused about the idea that they could buy an Elephant, and then did (and named it Bongo) and brought it along on their travels. The result of them doing this was:
- losing a bunch of money on buying food and stabling
- constantly having to think about how to bring it along to the next location
- being trivially tracked by everything so inclined
- having to deal with setting up camp with something that doesn't fit in the average camp site, let alone inside a Tiny Hut
- having to run out of their Tiny hut to protect Bongo when they were ambushed at night, instead of just waiting it out
- having to leave it behind with a bunch of magical wards whenever they approached any kind of structure
In the end, they had it for probably half the campaign and I think it got into combat only once. The rest of the time, it was just a huge headache to deal with all the logistical challenges of bringing a Huge Animal into any kind of place designed for Medium Humanoids.
They really loved that elephant though, so I'm glad they bought it ;)