Maybe they just want to go back and forth without adjusting their settings. I used to keep a walking foot on my mechanical just so I wouldn't have to get one out to use, just a thought. Also some have a straight stitch 9" throat just for quilting and use their small machines to piece. No one is suggesting that one needs more than one sewing machine, but it is an option for everyone if they can afford it. Its all a matter of opinion, its one of those subjects that you can debate forever. You can get by with one machine. I did for years on my cheapie mechanical brother being my only machine. The only reason I still have one is that many of the TOL machines are bulky and heavy, not easily transported for classes or travel, kind of a pain to move so most that own those own smaller lightweight machine