Agree with comment it's none of their business!
Bit of a long discourse to set the scene - I'll get to the point I want to make eventually
Once upon a time (and it was not long ago) people always had activities and interests outside of work and the home. Hobbies and interests of all types flourished and people got involved with groups etc to follow them. Could be anything from outdoor activities and sports, or history, astronomy, music, geology, etc etc.
Over the last 30 years we have seen this fall away. It doesn't matter what the subject is - local choir, amateur group of whatever type (astronomy, photography, geology, history, scouts) they all tell the same story - the complete collapse of membership from people in the 20 to mid 50s age range.
I'm sure there is a Ph.D in researching this! The reasons are many and complex. People are time poor. For people with families, parents are often taxi services as kids don't walk or use buses to get around (like I did); working days are often longer; people's commutes are longer - people used to live and work in the same town; television is an easy option, and so on.
I don't have a family, but there is pressure on me to work long hours, whic I try to push back on.
I have experience in two areas: choirs and amateur astronomy. I was invovled in administration of amateur astronomy from 1976 until 2006 (I started young
) from local level right up to national level. In the 70s, societies had a broad age range of membership from teenagers right through to people well into retirement. Many of these groups, especially in the large industrial cities, have a long proud history going back into the late C19th. Typical compositon was one third U20, one third 20 - 50; one third 50+. Nowadays it's more likely to be 10% under 25 and maybe another 20% covering 25 - 50 (i.e. one third covering everything U50) and remaining 70% over 50. Nationally, I used to get chairmen of local societies telling me the same story from across the country.
Choirs it's a similar story. Members U30 are rare - you do get a few. You do get younger ladies in the choir, but men U50 are very rare. I was 39 when I joined the choral society - I was the youngest man in the choir. For almost all of the time since (over 12 years) I have remained the youngest. It's only in the last year that that has changed.
Over the years I've talked to archaeology groups, geologists, ship societies, history groups, photography groups - they all tell the same story: the decline of membership from people of working age.
So, back to the main story
From my own experience at work, relatively few working-age adults are occupied in "hobby" type activities. The consequence is other people do not understand this behaviour and have no experience of their own to relate to. Consequence is they regard it as odd.
I'm a firm believer in individuality (that's a surprise given I play the viol!) and something which I find very sad is the way that modern society is so conformist. It was bad enough when I was at school to plough your own furrow (yes I preferred astronomy to football and I preferred Mozart to heavy rock). I think it's much worse now.
So, more power to your elbow and we should celebrate individuality and ploughing of furrows
. It's ironic in an age that "celebrates diversity"