There are a couple of reasons...
One reason is the characteristics required to become an elected representative. The type of people to become politicians (with a mixture of confidence and drive to change things or fight against something, as well as being outgoing and highly social) are generally not the type of people who are gamers. That's not to say gamers can't have these qualities, but if you look at it purely from a numbers perspective the likelihood is much smaller for a large percentage of the gaming world to have those qualities who also go into politics. Therefore, politicians can't connect to the gaming world as much because it's often so far outside their reality.
The other reason, in my opinion, is a generational thing. Most (not all) politicians at the moment are either baby boomers, Gen X or Millenials.
- Boomers at large weren't really exposed to gaming so don't understand it and see it as for children.
- People in Gen X played games but it was not in mainstream society, especially among adults - they might play them with their kids if they had them late in life.
- Early to mid Millenials play games more but there's still some social conditioning where there's some guilt associated with gaming (i.e. they don't want to be viewed as overgrown children, even if they secretly enjoy it).
- Late Millenials and Gen Z (or zoomers if you want) are more likely to embrace gaming as an adult as it's become more part of the culture.
I suspect as the older generation changes politicians will tend to be more accepting of their peers who still like video games since it's essentially their jobs to represent their areas.