I can't stand lag, inconsistent connections, or changing batteries, and with the exception of Airpods, every interaction I've had with Bluetooth devices leads me to believe the whole category of hardware is generally one big dumpster fire. So instead I toss a basic $20 wired logitech mouse into my bag, and it performs flawlessly every time I pull it out.
Yeah, I'm generally fine with that for that one example.
But the bigger problem is that I like being able to use friends' mice if I find myself without one, jack HDMI into my laptop for random conference room projectors (my MBP has HDMI out, it is frequently used), etc. I can carry around adapters/dongles, but I have multiple bags, and adapters don't always come with when I'm throwing my laptop into the bag I'm using that day. So the chances that I'll have something I want to use and can't because I just don't have the adapter on me are pretty high. This is a problem I never have on my 2013 13" MBP because of the port selection, but that I will if I don't change behavior if I get this 16" MBP (which I'm seriously considering).
