Because composers are artists and (I imagine) making art is not like a regular job. I know I would put a lot more effort into my job if I had to create something that people will enjoy experiencing and remember for a long time instead of spending all day sending e-mails and filling spreadsheets.
But why do big work when little work do trick
Because big pay for little work later. (Blizzard anyone?)
Because composers are artists and (I imagine) making art is not like a regular job. I know I would put a lot more effort into my job if I had to create something that people will enjoy experiencing and remember for a long time instead of spending all day sending e-mails and filling spreadsheets.
Working as an artist still has deadlines, requires working within constraints, and you have to negotiate with clients and suppliers.
Unless you don’t need to sell your art for a living, then yeah, you can do whatever you want. But that applies to any activity.