Maybe they think using many bitcoin
address then the transaction will be
more secure
There are many reasons behind using of so many wallet, some people use many wallets because the not satisfied with only one wallet, many poeple use multiple wallet for just secure their money to playing with many wallets, because if we store all our money in one wallet, and it got hacked then we loose our all money, so using multiple wallets secure us by loosing money.
Its always good to have multiple wallets, and people use it as different wallets have different features and security measures, but I don't think that its easy to hack bitcoin wallets.