[notsapiensatall]

I've been wondering the same things for the past decade. It seems like it's very hard to get your gene into the right place so that it will be expressed at the right time, with enough consistency to make a stable cell line.

Also, it seems rare to find just one gene that encodes a property or compound. Usually you need several genes to form a pathway from a common precursor chemical to your target result. That pathway will be leaky, and it may take resources away from other important chemicals that the plant's lifecycle relies on.

It sounds expensive and time consuming - plants take a long time to compile, and you can forget about reproducible builds. Plus, once you have your GMO, you'll be expected to take care not to release it into the wild, and in today's world, a decent chunk of people will oppose your product because of their personal beliefs.