Its never been a big deal to me.
A RL GF wanted me to do that - b/c she never had and she wanted me to "have all of her, parts no one else ever did"....
And, for an average size guy it makes you feel huge.
You know - that sound we hear in porn we imagine a woman making when we first enter her - that "omg its so awesome and big I can't believe it" that they don't believe and we don't believe but somehow we do believe?
Well, when you stick it back there - believe it - that is big enough! That was at least part of the attraction.