I have never met anyone who does cave, wreck or deep technical diving who does not use a 7 foot hose - except rebreather divers (who carry sling tanks instead).
if you're doing that kind of diving it makes a lot of sense. If you're newer to diving, and are still getting used to the underwater world, it makes less sense: the 7 foot hose takes a little getting used to, and can float up and get in the way a little until you're accustomed. It shouldn't be a fashion statement: use it only if the benefits outweight the entanglement hazard.
The benefits:
1. If your out-of-air buddy is panicked, the last place you want him is in your pocket. "Here's your air, now get away from me till you've calmed down!". Tech divers are not usually in that kind of a flap, but it's something to bear in mind.
2. The main reason for a long hose, though, is for going through constrictions. If you are on a short hose sharing air and you both have to squeeze through a tight hatchway or passage on a wreck or cave, you will want to go one in front of the other: usually, the one receiving the air goes in front. If you have tried it, it takes a little practice even with a long hose: I would not like to have to try it with a short one. These things are stressful at the best of times.
I use surgical hose to strap my secondary reg under my chin. I would recommend doing this whether you use the long hose method or not: then you always know where it is when you need it in a hurry. And it prevents your secondary dangling down in sand and getting gunk in it - or becoming an entanglement hazard when it gets caught in something.
Don't tie the secondary too tightly to the necklace: if you pull on it it should come loose.
In the end, it's your choice. If these arguments don't convince you, don't do it. Look at other people's gear: ask them why they chose a piece of kit, and why they rigged it in the way they did. But this above all else: never listen to ANYONE who tells you there's only one way of doing things. Adjust your equipment set-up little by little, getting used to each change before you change it more.