Also another reason for multiple jobs- splitting up the vbk files.
Most of our servers have 10 or so partitions, anywhere from 2TB-4TB each, and usually about 50% or more of those partitions are full.
Being able to have multiple jobs would allow us to have multiple vbk files for that server, thereby spreading the risk of corruption taking out the entire backup data for the server. Plus, it makes it easier to recover from corruption. 1 of the 4TB partitions' backups got corrupted? Okay, not too terrible, just reseed that 1 job.
If there's 1 gigantic 50TB vbk file and it gets corrupted? Redoing that is a major ordeal.
Also then that means on really big servers you could have multiple jobs pointed at a SOBR repo, thereby making more efficient use of your storage and spreading out your risk of data loss on your backups.