Alot of reasons but I will say I've done the same in the past...take last year for example I didnt take any tuning gigs from September through Late January...which I think is about the time I did your tune if i remember correctly
Unfortunatly I don't have a comfy garage to work out of and rolling in snow to install a wideband isnt my preference.
There are alot of other reasons that I really don't want to get into on a public forum, but definitly nothing "fishy" or what have you thats for sure.
Like I said maybe come summertime I'll start back up, but for now Im just gonna concentrate on helping some people tune their own cars for a dinner and gas money here & there and nothing more. That in itself is more gradifying then tuning other peoples cars in my eyes.