The Nintendo Switch does have a WWW browser, solely for permitting access to Internet connection points that require loading a WWW page and performing a certain action as a prerequisite for use.

It's appalling an entire WWW browser would be necessary for connecting to certain Internet access points, but that's the current state of things.

In any case, someone has already achieved arbitrary code execution through it, but it was sandboxed anyway.

I imagine that that’s a selling point for parents. Maybe that’s the bigger reason?

Yes, because most likely that browser was implemented in C or C++ and the exploit was achieved via a memory corruption bug.

Also this is an orthogonal issue, the console wasn't designed to have security exploits to start with.