My amp has 2: a serial, and a parallel. I use them both, and they do have advantages. I could work around not having them.
Some pedals sound better up front , while others sound better thru the loop . It's all personal preference .
I just set my pedal board up in 4CM to stick a Flanger in the loop to cover Spirit Radio in one of my bands. In front of the amp wasn't cutting it. Reverbs and delays in the loop really are better. When I had a rack, and a JMP-1, the reverbs, delays and mod effects were in the loop and were glorious. Meanwhile, back in those days, I thought a phaser was dumb. Not until I put it on the floor in front of a TS-9 did I discover the tone I liked from it.
For me, vital. Need the option of switching off the effects loop, and getting unaltered tone. Don't like delay in front of my amp.
No Loop = no 4CM. Parallel loops are the deal breaker for me. The one in my old DSL401 drove me insane when I first cottoned on to 4CM. It had to go.
