As mentioned by @moamirkalali there are situations with gear where, in my case, I was changing from a SS system to a tube system (because of equipment failure) but wanted to keep my speakers (KEF Reference 205/2’s) that are a bit power hungry…
Going through the assortment of tube amps offered by McIntosh (my system is all McIntosh - can see in My Systems) the choices were considered based on power supplied, price and esthetics. I chose the MC275. However, unless mono-blocked didn’t produce enough power to adequately drive the KEF’s and individual REL S/812 subs. I don’t play music super loud but occasionally crank it up for a particular track of music. It’s nice to have the power when you want it. At the mono-blocked MC275’s 150wpc the power delivered is adequate for the KEF’s but not overdone. My system sounds GREAT, by anyone’s standards.
Go mono-blocked if it suits you. Don’t worry about whether it’s a popular thing to do or not!

