It's a small tool for generating variations on a chord progressions, not writing songs or coming up with melodic ideas. No need to make everything complicated.
I think generally it just muddies the waters from a technical perspective. While it's possible to do a simple version of this quite easily, it's more prone to failure than you would think and anything more complicated than plain text isn't so easy. I think given Tina experimented with this in the past it's likely they'll try to make this work at some point, maybe it's on their roadmap.