She's previously stated on this board (I think sometime last year) and on twitter that she absolutely loves anal in her personal life and does it all the time. And that her not doing her another one was simply because companies weren't paying her the rate that she demanded, but otherwise she would love to do it. Now that's all perfectly reasonable in theory, but that's why I always compare her career to Asa Akira's and which of their porn business models actually makes them more money in the end. Asa accepts less money than Rachel to do a lot more anal scenes (tho obviously she's paid much more than a normal non-anal b/g scene), but also loves it in her personal life anyway, so its a win-win for her. Meanwhile, Rachel will ONLY do anal for a HUGE amount of money and therefore she's so far only found 2 companies in the last 2.5 years willing to pay that amount of $ and therefore makes far less money holding out for the giant paydays even though she also loves it in real life as well. So of these 2 pornstars' business models, 1 of them makes business sense and the other doesn't - especially considering they both say they love anal and they both obviously enjoy making more money.
IMO its must just be ego that's keeping Rachel from doing more anal and therefore making more money. She'd prefer the prestige of occasionally making a porn company "break the bank" to higher her services over the actual reality of making more money over time. Lets say there's a $1,000 pay bump in doing an anal scene. If Asa has done (lets say) 25 anal scenes in 2.5 years, that's an extra $25,000 that she's made doing the same number of scenes she was already going to do anyway and for doing something extra in a scene that she already loves doing anyway at home. Now unless Rachel (who's probably made 40-50 scenes in that same time frame) made $25,000 for that single 2nd anal scene alone (which there's no way she did) then I don't think her plan works in the end (even if it is a noble effort to try and get companies to pay their stars more). At some point the free market has spoken.