Sometimes you can downsize - for example my 16 x 75 is too long and I rather have a short bed lathe in better condition or one with more beefy bed - 16 x 40 would be much nicer. Heck even 14 x 40 that was "heavy duty" should be OK as long as spindle was still D1-6.
Or get another lathe that is smaller - hassle of moving large machine is a LOT of work. Trying to sell it, move another one in... HD 10x20 I got as a supplement is great - it is accurate and very nice for small parts. Besides with two lathes now one can tackle fixing one while the other still makes parts.
Also one can do things better then the other. I have to figure out how to tighten the cross slide on the little one as with loose cross slide I cannot do parting on it.