I used to have a GBA. But these days… no. A significant reason is that, since I don’t usually carry a bag and it’s often warm enough not to need a jacket, I simply have nowhere to put a handheld system when I’m out and about. Keys, wallet, and AirPods go in one pocket, phone in the other, watch on my wrist; that’s about the limit of what I can carry besides holding an extra device in my hand, and I prefer to keep those free. When I’m not out and about I have access to my laptop with all of Steam, GOG etc, and a full controller, so a handheld feels a bit redundant.
The other reason is that interruptions can be common on public transport. Mobile apps and games are designed to be stopped and started instantly, and usually require less commitment to play a game. Handheld games are more like small console games from my experience, so are perhaps more suited as a console replacement for those without a TV or gaming PC/laptop? I’m interested to hear how other people fit these different devices into their lives.