> I'd argue that being slow and using a ton of memory has more to do with (very) poorly optimized websites rather than blaming browsers as a whole.

A web browser is a huge platform. Audio, 2D and 3D graphics, file handling, network requests,... A lot of code while your application needs are tiny. That is wasteful and a security risk.

That's really only argument against shipping a browser with your application. For ordinary websites (or WebViews) that's not really a concern because it is shared and automatically updated.