The issue is that they store your details. They could quite easily make an offline version where you never transmit data to them. This would prevent any data leaks.
If you store something that people want to keep secret, expect others to want to steal it. The more secrets you store, the greater the desire to steal.
FYI: For SSH logins you should be using keys not passwords, and I would say something about FTP, but I know too well that clients stupidly ask for FTP access. because they have no clue about security.
Sure, no password have (allegedly) been taken, but that is this time. It just take one real data breach for your passwords to be taken. What if these allow access to very confidential information? What will you explain to your clients then? "I kept my passwords externally for convenience"? I doubt they would appreciate convenience coming before their confidential information. If it is confidential information, as a client, I'd rather it be stored locally rather than externally. I mean, sure, if the information isn't that important, like maybe some forum account, use it. But for serious data, I just feels like you are going to a guy with a target on his head and saying "Hey, can you hold on to this for me."
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