Can I ask it around the other way. 'Why would you wear your uniform when not about to report for, or actually being on duty??'
As soon as I hit the carpark all 'pilot' identifying guff comes off, but then again I also tell people at social gatherings that I sell 'UPVC Piping' as I became totally sick of people venting their 'bad' airline stories or insisting on telling me I get paid far too much money for simply pushing a few buttons