I hate extras for several reasons:
1) Because you've got to pay them upfront and then you feel compelled to have them (to have your ROI) even if in the heat of the moment you might have fancied the meet to go into another direction. This takes away the freedom from the meet and turns it more into compulsory figures than free style to use a sports analogy. As others already stated it'd be awkward to say at the end 'hey we didn't have XYZ, can I have my money back'.
2) it also feels like the girl is offering them to make money but possibly does not enjoy that particular type of service. Nothing worse that her telling you she really loves XYZ and then once the notes have changed hands you realise that it couldn't have been further from the truth. Total wood killer to feel cheated. Because of the once bitten twice shy adage, extras act as a red flag for me, even if not necessarily true.
3) I guess that by having extras it further highlight the transactional side of things and takes away the real life partner experience we're after. I am not kidding myself, seeing a WG is a business transaction, no doubt about this. Yet (whether purely GFE / vanilla or more PSE / niche services) we'd like to believe the connection is genuine even if only for the time it lasts. a bit the same as the difference between a girl providing a great service with effort and enthusiasm compared to one just going through the motion but clearly not into it. Having extras is a bit the same for me. It rubs my nose deeper into that transactional side of it compared to an 'all inclusive' experience where it less obvious (even if just as transactional I am not fooling myself)
4) However carefully thought and 'justified for the extra effort' the pricing structure of extras being usually purely additive it very easily transforms an affordable or reasonable punt into a totally prohibitive experience.
