Your domain is the one asset that is genuinely hard to recover if it ends up in the wrong hands. Everything else can be rebuilt.
Lose your website files and you can rebuild. Lose your hosting and you can move. Lose control of your domain and you lose the address every customer, every business card, every sign, and every search result points to.
Recovering a domain from an unresponsive registrant is slow, sometimes impossible, and always happens at the worst time.
The person who built the site years ago registered the domain in their own account, using their own email. They've since moved on and don't respond.
The site still works, so there's no emergency — until renewal comes around, or you need a change, and there are no options. The business either negotiates, waits for it to expire and hopes to catch it, or starts over on a new address and loses everything built up on the old one.
That last one catches people out — expiry warnings go to the registered email, and if nobody reads it, the first sign of trouble is the site going dark. Catching that kind of thing before it becomes a problem is part of ongoing updates and edits.
The site stays up the whole time. Handling this is part of the service, but the account it ends up in should still be yours.
Recently registered or recently transferred domains can't move again immediately. There's a lock period. Worth checking before planning around a date.
Privacy protection is worth having. Without it your name, address and phone are in a public database, which is why new domain owners get a wave of spam calls and fake invoices.
The domain is the address; hosting is the space. They're separate services and can live in different places. Keeping both in accounts you control is what makes the site genuinely yours — the same reasoning as owning your source files.
Describe what your business needs and you will get an honest read on what would actually help.