Question: During the battle of hoth, we do not see any snow troopers until they have entered the base, what was the point of the trenched rebels if they only got slaughtered by the AT-AT's?

It's been bugging me for ages. I started re-watching Empire Strikes Back on the train yesterday and it got me thinking. Whilst the battle of hoth is epic, you also don't see any ground assault troopers, only AT-AT's which are miles away from the rebels.

So the rebels in their trenches were sitting ducks. What was the point of being there? Why not hole up in the base and let the snow speeders take care of the walkers?