I have verious thoughts on this. Halters can be very dangerous to get hung up on things.
But I agree, there is also the problem if needing them in an emergency. The barn is on fire and you need to get them out right away and they are freaking out so hard to get one on them, there is something going on outside that is freaking them out and you need to bring them in, etc. I know a decent amount of people who will keep breakaway halters (that actually work) on their horses. I say that actually work because they trim them down even more and they have broken plenty of times. But when it comes down to it, if you are going to have a halter on your horse that breaks away easily enough for a stuck foot-in-halter to break it, then its not much of a halter for leading a scared horse. The last thing you want is to be leading your afraid horse, them to resist some, and the halter to break and them run away.
For these reasons I have two possible suggestions.
For horses that really are hard to get a hand on when they are afraid, I would put a breakaway halter on, or even better, a break away collar. They make horse collars (just a loop around the neck), or you can easily make your own that breaks away VERY easily. This can help you get a quick hand on your horse for long enough to put a real halter on them, or to throw the lead line around the neck/nose if your are really in a hurry. For hard to catch horses I think this is the best solution.
If your horse isnt that hard to get close to even when its afraid, then leave the halters off and learn how to properly use a lead line as a halter. In order for this to work your horse needs to be properly trained, so that it has absolutely NO fear of a rope being tossed around its face. If you are going up to your panicing horse, you NEED to be able to toss the lead around its neck to catch them without them ducking away.
Not being able to catch a panicing horse is just as dangerous as having a halter on. I have seen many horses injured this way as well.
Having that said, leaving a halter on a horse is a big no no. at a minimum have a break away halter, but i would highly suggest having either nothing or a very break away-able collar that you dont use for leading.
just my $0.02