Maintenance plans are used by those that don't have the coding skill to create backups, defrags, and other functionality. I am weaker on creating code for replication and log shipping so I use them only for that. There will likely be a day when I won't use them for those functions either.

On every project I have been on as a consultant where I found maintenance plans in use had un-recoverable databases, massive collections of log backups but no full backups, routines that drop indexes and lockup that database in the middle of business day, etc...

I HATE maintenance plans because they are too easy to use by the profoundly ignorant. They are similar to giving a small child a fully loaded and cocked semi-automatic handgun and leaving the room.

Never use them if they can be avoided. They are too harmful because they claim to help the business and end up betraying that trust when the database is unrecoverable.