IMO because each wallet has a unique advantage unique in it and of itself, for example electrum and blockchain are very fast and relatively easy to use, other wallets like armory or bitcoin core are more complicated but relatively more secure.
yeah it's possible. people want a different wallet facility. I myself use electrum and blockchain
both have their respective advantages, and I can take advantage of both
Exactly, mainly I use blockchain, but when I have to gamble I use multibit, as the bitcoins sent on betting sites are instant, where as sending from blockchain is bit time consuming and it might change the odds meanwhile, so its better to have multiple wallets.
Yes everyone uses many bitcoin wallet different for different uses.
This was done in order to remain safe and secure bitcoin.