people are using so many bitcoins wallets just because they dont want to have all of their coins just in one wallet because not every wallet is very trusted by people so that is why they use more wallets to be sure that not everything can be stolen.
yeah maybe people do not believe in a wallet ot they just avoid theft great. because if you keep all of your money in one wallet
of course it would be very risky when your wallet in the hack. so it would be better if you use a lot of wallets
There is an old saying: don't put all your eggs in one basket. This is suitable in bitcoin community, we have mtgox, mintpal, cryptsy, bitfinex hacks, or down eventually, the clients got screwed by them and lost money, so don't just put your btc in a wallet, make deposit on more wallets, this is very secure way to avoid one wallet site be compromised