I’m building up a road bike. Do I need to fit barrel adjusters on the gear cables?

Got 105 and Ultrega and not needed as have adjust on mechs

Having said that I still like them to adjust on the fly but in theory once cable has settled down shouldn’t need to do this…less is better and with current road trends would be inaccessible anyway

I also have Ultegra (6800) on my road bike.
As the front mech doesn’t have an adjuster, and I was building it myself, I fitted an inline adjuster to the section of cable between where it emerges from under the bar tape and enters the frame, near the top of the down tube.
I’ve only had to tweak it once or twice, in 5 years, but it is very convenient.

(The rear mech has an adjuster built in, so didn’t install an inline adjuster for that)

I have an inline on the front but nothing on the rear because there is an adjuster on the mech. You probably don’t need one on the front but it makes things easier to set up in my experience. And, as above, it means you can tweek easily as things bed in and wear.

I had them on the Merlin from new.

I’ve two more sets in the shed now for when I change cables on the two other drop bar bikes.