A store might need multiple addresses, but they can all be contained in the same wallet.
if you have coins all over the place why not just send them to the 1 wallet ?
Some reasons:
- To keep coins from different sources separate. When you spend coins the transaction inputs can be from any addresses in your wallet. Since all transactions are public and some of the addresses may be publicly associated with you people can find out how many coins you own and what transactions you make. So to avoid all that it makes sense to keep bitcoins from different sources in separate wallets.
- For security reasons you may have multiple wallets. Hot wallets on your PC or mobile and offline wallets for larger amounts.