To be fair to your first point, if you set up a bouncer or use a client inside of screen/tmux you can absolutely catch up on what was said earlier in IRC.
Really? I just leave irssi running on my linode, I don't even bother running a local client most of the time, I just SSH in and use it. The only exception is when I'm on mobile, and I have irssi-proxy running for that one special case.
I think part of this debate is that for some people, the above is a pretty normal and easy way of doing things, and for others, it's a large barrier to entry.
Which is additional configuration to pay for and/or take the time to set up. And that you have to think ahead enough to realize you need this before you actually need it.
