The words "I love you," are said too lightly. They always have been. To steal a phrase "love is never having to tell your partner 'I love you, even though you'd better if you do."
Unfortunately some people don't understand that. Just exactly what does "I love you," mean?
Without all that goes with it, loyalty, trust, sex, safety, support, and in some very rare cases, an acknowledgement that your lover is also your best friend, they're empty.
On the other hand......when someone says "I love you," unless it's just gasped out in bed (sorry, I'm not trying to be indelecate here)...and then it might or might not be true, it is very bad form to say "why?" Under normal circumstances, even if you're just lying in bed with them after you have sex.....or better, walking down a boardwalk (we have those in Jersey and in California....and elsewhere, I suppose).....don't question it. Love is NOT the demonstration of physical affection (or at least not to this old married man). And as one comment above said....I love you is not a question (that guy is married to a very wise woman) Remember:
Your partner probably:
1. Had a hard time saying it the first time....or as age1600 said above, have made a supreme effort and committed to an act of faith that you won't laugh at them (not that I know why it's hard for her to say, but this is me talking)
2. feel all the other things, but use that phrase to put it into words
Asking someone "why?" does the following:
1. it implies "why should you, I'm nothing to love," which is your problem, not his or hers
2. and it is throwing cold water in the face of someone who is trying to express a very deeply felt emotion.
As aspies (most of us) we have to remember that NTs (and sometimes other aspies) do not require an explanation for everything. Especially if your with an NT (as I have been for 20 years), you have to resist the word "Why?"
When my NT wife told me she was sick (when we were first married), I'd say "Oh, I'm sorry." And she'd reply "For what, it's not your fault." Which was a dash of cold water. And when I didn't say it, because I thought it bothered her, she would say "don't you care?" We worked it out, but it's the same thing with "I love you."
I'm just sayin.
Btdt