Asthma you see the specialist- wouldn't see a GP for asthma treatment would you??? Would you have a GP do your annual colonoscopy???
Actually, yes. DS's GP diagnosed and treated his asthma for years. My NP does all my annual testing with the exception of mammos and a recent abdominal u/s I needed. My DD was referred to an ENT specialist by her pedi and I ended up closing my cases with both of them and going to a GP for her as well. For her surgeries I did use an ENT from Mass Eye and Ear but for her follow-ups and regular visits, the GP was great! Going to one person for all your basic ailments makes much more sense to me IMHO than having several doctors, each one treating something different.
Once you get to know and trust a doctor (GP or NP) I see no reason to go elsewhere unless THEY deem it necessary. And... specialists for common ailments is one of the reasons our insurance rates are so high.