I was checking a random address in blockchain.com, there are alot of transactions that is done over this address. While in the website it is mentioned that the address is changing everytime! So it means that every address should hold at most one transaction!
You need to differentiate between the website's wallet (Blockchain.info-wallet) and the blockchain itself.
You are allowed (by the bitcoin protocol) to make as many transactions per adress as you want.
But wallets try to make it as comfortable as possible for you and use one adress only one time so that you are acting as pseudonymously as possible.
You have probably seen an adress that has not been handled within such a "only one time"-wallet.