People who've been riding horses for years: why is it so necessary to mount the horse from the left?

You can train yourself to mount from the right. You would also have to train your horse to accept being mounted from the right.

It's not a bad idea, actually. But few people do it.

Mounting from the left was a tradition started by people who carried swords. The right-handed majority hang the sword off of the left hip. It's easier to mount if you don't have to swing the sword over the horse with the leg.

It isn't actually. . . horses should be trained for mounting from both sides.

Because of the sword thing, it's tradition to mount from the left and something both horse and rider become accustomed to. Many people though mount from either side. Be sure your horse is used to it before you try it out of the blue. They may wonder what is going on..... Horses many times have a strange relationship to right vs left. Just because they know the left does not mean they know the right side.

It comes back to when people carried swords.

Most people are right handed so the sword was worn on the left to be able to draw it.

Trying to get a sword over the horse was not sensible.

It also ties in to the Romans driving on the left. Therefore kerb side.

There are good reasons to drive horses on the left side if the road.

Riding side saddle there is no stirrup on the right hand side.

You should be able to mount from either side.

We always used to train the horses to accept mounting either side and mount both sides.

It's more comfortable for people to use the left. If a horse was traded or sold, how would you know what the animal had been taught? That's why they are all taught the same way, in general.

It's not, at all, necessary.

The horses are trained that way.

I've heard it's because people are right handed. If you mount from the left, you can use your right side to balance yourself better. As for why you HAVE to always mount the horse from the left, it's probably because the horses are trained that way and you don't want to break their training. I'm pretty sure a simple Google search would answer that for you.