Well - (constructive, yet respectful criticism to follow) - from what I am getting here - you are basically suggesting a race that reproduces asexually - but that requires sex , particularly merely arousal and orgasm - to become pregnant. Barring the obvious pleasing advantages of a coupling, to be honest - it would not be necessary at all from a purely evolutionary or biological perspective (if you believe in evolution, or subscribe to it's tenants).
Firstly - over time - nature would select it (sexual coupling) out completely anyway, (like the need for a tail bone - or an appendix), - if for no other reason than the balances of cost versus benefit would kick in. Sex is a very risky business for a lot of different species - let alone humans - and if an entire species doesn't have to really have sex with others in order to reproduce, but instead - only needs arousal and climax - then the potential cost of coupling would outway the benefit. Most social bonds would eventially develope to be formed to aquire mutual benefits in other ways than sexual, romantic, or procreative means - possibly friendship, adoptive familial, religious, political, or cast based relationships would fill the void. Some might even argue that the negation of the need for sexual pair bonding would result in the collapse of a civilization whose roots were founded upon the concept of a nuclear family unit per se. It could be vaguely argued that since there was less reason for intimate interaction - minus that dynamic - the species in question would become more solitary and territorial, and less social - resulting in "devolution".
Secondly - males would eventually become almost entirely extinct, occurring only rarely as an abberration. A more realistic perspective would be if you had a species that would change gender, like some amphibians do - that way you could eliminate the "human" procreative norms of this species - yet still give it a tangible reason for remaining intersocial enough to maintain the stimulus for keeping some kind of civilization going. As an example - the entire history of human civilization can be effectively delineated down to the level of the baser family "clan", or family group structure. If you remove that dynamic - with it's core foundations as being heterosexual procreative pair bonding (biologically / historically), then eventually - like removing a tiny hinge pin that may be seemingly insignificant, but that holds an entire bridge together - you would cause that civilization to - at least ever so slowly and gradually - collapse.
Just as a social scientist might argue that homosexuality - at least currently - may act as a positive, yet statistically tiny defense / check point against overpopulation, the same scientist might say that the total elimination of heterosexual interactions would send us careening into extinction. However - if no pair bonding at all is necessary for a species to survive - then either argument becomes moot.
You are suggesting a species that also interacts with other species sexually in order to facilitate arousal to initiate gynogenesis. Now although instances of interspecies "nooky" in nature has been observed before, and is certainly not unheard of, it is still not a viable concept as an "across the board" trait or norm, because it would violate and endanger a lot of basic survival strategies.