I'd say Accordions - probably no. But then, the traditional soviet bayan is exactly that: MM in the treble and no registers all around.
Other harmonikas (melodeons, bandoneons, etc) - yes, especially if they are diatonic, as you get away with something like a 32x18cm (or 26x26 in case of bando) box, yet, still get about 3 octaves + accidentals + reasonable bass selection for home keys. Fitting even 3 voices can make the box size explode.
A bando with LM in the bass and MH in the treble is enough to keep you busy for your whole life.
I'm currently playing a hromka with just LM in the treble and I'd say even this is enough to keep you busy for years.
One I'm about to start tuning is LMM, no registers. It would probably be nice to have one on each voice, but there's some joy in simplicity. Registers waste air...Ok for a full-sized accordion, but can become quite noticeable on a small melodeon.
To me, some boxes have timbres that I can listen to all day, 7 days a week. Typically with Russian or German reeds inside. With Italian reeds I get tired of the rich, overtone-loaded timbre very quickly and can't wait to press the register switch, half way through the piece (or the song

).
If you ask me, I'd start with getting some high-end reeds, then throw away some of the notes (you don't
really need all of them

) and only then you can start thinking about removing register sliders
And it's probably closer to the comparison of driving a motorhome vs driving a classic motorbike.