Some people need it, some people don't.
Personally, I'm of the opinion that riders should learn to be balanced enough with their own seat to ride 2-handed even at high speeds, without yamming on the horse's face. This allows the rider to more effectively guide the horse and maintain equal balance. It also prevents over-bending by using the outside rein as a supporter. Overbending the turn can cause serious balance problems, which result in knocked barrels or slow turns.
A person who just sends their horse into the barrel, drops to their horn and pulls with the inside rein is pulling their horse out of alignment from head to tail and thus off-balance. This often results in cross-firing, loss of momentum, and dropping onto the forehand. Also, specifically, will cause a horse to start shouldering a barrel, slicing off the backside of the barrel, and just generally slowing everything down.
I decided to go hornless in 2008 when I came out of the Congress polebending arena and couldn't move my arms, having bashed the bejeezzus out of my elbows during the run. Not to mention, typical western saddles didn't fit my very hard to fit little mare, so I decided to buy this instead:
Wintec Aussie Pro Stock, Western Fender, 17" - $1650.00 US. "Little roan mare, aka Wisher" is modeling.
It was a hefty price tag, but well worth it. Not only do the thigh-blocks keep you from popping up out of the saddle, but they allow you to ride effectively when two-handed, or losing stirrups. If I lose a stirrup, I lift my leg and lock myself down with the counter-pressure on the block. That feature allowed me to run 6th place in two pole runs over a week at a big NBHA provincial show, instead of bombing out.
Not to mention, for horse-comforts, the saddle is lightweight, has changeable gullet width and CAIR panels (air instead of fleece or flocking), a flex tree, and since it is built without skirts of any kind, you've got tons of hip room for short-backed horses. The panels are set quite wide and disperse pressure well over a broad/wide or flat back. The gullet is rather high, so this saddle is EXCELLENT for horses with tall or prominent withers (or just withers). However, it does not sit on mutton-withered or "no withered" horses well due to this. My horses feel smoother running in this, and smoother in their turns. My gelding Turbo loooooves the freedom he's got, and I loooove not getting blown off the back of him.
Video of the saddle in action with Turbo- 2nd in 2D, Black Gold Supershow 2009, out of 130-140ish horses. This run was smooth as silk and felt like "whoooooooosh, turn... whooooooosh, turn....." Just really effortless.
So yeah, I for one am all for two-handed riding and ditching saddle horns. So is Edwin Cameron, and a few other people I know, including my little sister (who 2-hands Poles and has 3 Congress championships to back her up). One of my recent students is a Dressage rider turned barrel racer who has done all of her lessons so far in her veeeery pricey Dressage saddle and a bitless bridle. She rides beautifully and her large pony is already turning like a top 1D horse, progressing much faster than I expected in a short amount of time.
I wouldn't expect a little kid or novice rider to be able to run 2-handed. It does take skill and it does take a lot of natural balance, an independant seat and independant hands, a strong core, strong legs and back. And the barrel racing equivalent of a crest-release. lol
But then again, I wouldn't want them to run faster than they are capable of, anyways, because horn or no horn, it comes down to safety. If they are really going to fall off without grabbing their horn more than half of the course, they need to slow down and get some better riding skills. The horn at most is there for support when needed- such as on the departure from the barrel when the horse is gunning it and you're flying out the back of the saddle by sheer power alone. I can actually grab the gullet of my saddle when needed. My sis will grab her horn usually on the last turn of a run, because her Fattie launches her about a foot out of her saddle. LOL
The horn should not be over-used and really should only be used when you are more than halfway through your turn, and your horse is well clear of the barrel.
It should not be used as a crutch to allow your novice rider or rider with poor balance/seat to run faster than what they are capable of running safely.
I feel the same way about velcroing your 4-10 year old into a saddle on a big powerful horse. If they can't stay on without the velcro, they shouldn't be going that fast on that horse.
In conclusion- you do what works for you (within reason). If you feel just fine, your horse feels just fine, and you are running good clean runs with two hands, or one hand, or both, or your legs, then do it. Other people are opinionated and need to keep their opinions to themselves unless they are asked to give it.