If you are paying for backups at the same company that hosts your sites, you can absolutely NOT trust that they will be OK. This forum is full of complaints about companies going out of business without warning (which I have personally experienced, twice), billing disputes causing people’s data to be “held to ransom”, and hardware failures that affect backup restoral. Always have off-site backups.
If you’re asking whether independent companies can be trusted – generally yes, if they’re backup specialists. But you should never rely on just one backup. Human error is the biggest cause of data loss and backups can be deleted by mistake just like anything else.
All hard disks (including SSDs) fail eventually because they have a limited number of writes. That means sooner or later you can be certain that you will need to restore a backup, and at that time it will be your only copy of your data, so the first one doesn’t really count as a backup, if you see what I mean.
I have personal experience of a site that had no less than four independent backups, three of which were found to be unrestorable when it came to the crunch! I vividly remember that one backup used UpdraftPlus (to Google Drive) and another used Amazon S3 and neither of those was showing any errors in the backup logs but neither had restorable backups. I have since stopped using those services. Another backup was showing errors but the reporting wasn’t working because of a credential change (the same change that caused the backups to fail). All were working fine when they were first set up but hadn’t been tested regularly enough.