Most professional pilots do have a genuine interest in aviation at the start, otherwise they wouldn`t go through all the crap needed to gain their ATPL !
I will say however that the interest CAN wear off when you`re working in that environment everyday, so much as to say it gets fairly tedious at times. I think this is probably a major reason why "spotters" get that reaction from ppl working within the aviation industry especially. We simply just forget what we were like at the start and don`t understand how ppl can get so enthusiastic about it !