Because that's what it is. I think some of it might have to do with the limited content of the petition itself (a pretty short description about "customers being robbed" without any broader ideas suggested by the campaign) and some with the fact they get plenty of petitions so the first reaction is to stick with what's already there. That's my guess at least.
I hope that if this petition reached 100k signatures and went to a parliamentary hearing there could be a chance for a more nuanced presentation of the topic but who knows, maybe I'm just being naive.