E.B.
My son sounds a lot like your son (he's older, now, but at 17, their stories sound similar). Mine was also a good kid, not in trouble, doing well in school but suddenly, our family was well, embarrassing? boring? dull? His girlfriend's or buddy's family could be eating the exact same meal as we were at the exact same time, but somehow, the way they ate or the way the lettuce was arranged in the salad was just SOOO much more interesting than us!
It stayed that way for awhile. He went to college and of course kept in touch, but still, it seemed like he didn't need much advice. I let him have his freedom and, like you, it made me sad. With my daughter's medical emergencies, I had depended a lot on my son when my husband was deployed. And it was slipping away.
He'd call, but usually for money, or a favor. I sometimes would dread seeing his number pop up on my screen. What did he want now?
And then, one day, he called and he said "just thought I'd say hi. What's new?" And he didn't ask for money. And then, he drove by and said "wanna get a drink and a pizza?" And now he's in his 20s and he calls to just talk, or to tell me about his job. Last year, he had a one week vacation and asked his dad if we could help him with plane fare to come visit us! That was his choice (we didn't mind helping with the fare - it's a very long trip and really expensive to fly to here) and we had a wonderful week.
Sometimes I attribute it to maturing, on his part, and to relaxing and waiting patiently, on my part.
Stay available, don't be too shy about telling him you miss spending time with him but don't do it in a way that makes him feel like you're desperate or heart broken or totally lost in life. Stay patient, and loving, and show him that you're proud of the young man he's becoming. When he asks for advice, don't dump the entire advice bucket over his head - try to just stay focused on the issue he asked about. Make him his favorite cookies.
It will be for a season, but only a season. Be grateful that he can be independent and believe that the love you have for him will not be forgotten.