I get what you are saying about the sunk cost of biomods compared to other less expensive items that do give a minor stat buff.
On the other hand, biomods are socially divisive. Where as one person might think a biomod is cool, another person might actively hate the biomodded person.
My opinion on this, and it's just my opinion, is that if we codify a stat buff for biomods then we are effectively implying that biomods are the pinnacle of attractiveness. In other words, EVERYONE is going to find biomods attractive.
I think you can counter argue that the other stat buffing items in game might not have a universal appeal. For the one item that I am aware of, it is thematically appropriate due to plenty of 'cyberpunk' lore that precedes Sindome.
As I said above, I (my opinion) don't think that biomods fall under that category of 'universally appealing' due to how socially divisive they are.