If you bin someone simply over a low sex drive, then yes that seems a lot like you're using woman purely for sex.
Not really...
Using a women purely for sex would indicate that 'sex' is the only part of a relationship I am interested in. Which is not even remotely the case.
If it were the case then surely I would be the kind of guy to nip round the girlfriends, sleep with her, then bugger off home or go out with the lads etc....
It is merely accepting that there are differences between two people and moving on rather than living in denial. It's akin to pulling a plaster off quickly. There is far less hurt involved if you are honest and break up with a person if you realise they are not what you're looking for.
Far too many people allow a relationship to turn sour, put up with arguments and unhappiness. Then get married hoping it will solve things.... it doesn't.... Then have children hoping it will bring them together.... It doesn't.... Then after a few more years get divorced leaving a broken home and a huge mess to clean up. Twenty years down the drain and and a huge impact on any children.
Not good enough.
If the differences are substantial and are visible early on, then get out. The girl can move on and you can move on with your head held high knowing that you haven't cheated and have actually done the best thing by the girl herself.
Using somebody would be continuing in the relationship knowing that there was no real future because ultimately those differences will come between you at some point. No matter how good intentioned you are.
Your current girlfriend for example, what would you do if she wasn't up for sex every day? Or her sex drive started to slowly diminish?
I have been with her long enough now for emotions to become involved. I would not leave her, we would talk it through and probably be able to find the root cause and deal with that.
What you seem to be ignoring is that I'm talking about relationships that were less than 3 months long and have stated so on several occasions in this thread.
It is no different to leaving someone early on because you realise that you have nothing in common or that they are natural moaners etc...