I see a lot of posts saying people have written/are writing their own game engine for LD. While I hugely admire the technical skill involved, with so many free and polished engines out there (Unity, Unreal, Corona, Defold, Love2D, Lumberyard etc. etc.) it seems to me like reinventing the wheel, and time that could be spent just making better games. I can understand it for big AAA companies that build a targeted engine to make a specific type of game, but indies/hobbyists with limited spare time?

Is it just a case of 'because I can?'. I get that it would be fun and satisfying, but is it more fun and satisfying than making the actual game?

A parallel to me would be a composer who instead of buying instruments builds their own, or instead of using Logic or Cubase writes their own DAW.

Not attacking anyone, and probably just a little jealous, but interested in what the attraction is?