The interface is that way for a reason. What do you think that reason is?
Because it was the easiest thing to do given the existing codebase at the time and the game is written by uncompensated volunteers.
This to me along with the preceding posts, portrays a sentiment here that the developer shouldn't have their own interest in the game. That their choices couldn't be valid ones to make because they prefer it that way themselves, and are willing to do the work. Rather the undesirable way to do whatever it was they decided to do, must have been the easiest way. Or a mistake that needs to be rectified.
It's a vein that runs through a lot of the threads posted on this forum. Where various posters (not yourself) often betray an entitlement that games be done their way, and talk rabidly with their hands over their ears.
Uncompensated volunteers? Hmm. Really?
What you say here is a fair point and it's fine as far as it goes. Obviously, I can't deny it's possible that someone actually likes the multi-window angband interface better than various obvious alternatives outlined above and that this someone might be the guy who wrote it that way. However incomprehensible it is to me that someone would like angband this way without it being thrust upon them as the default interface, it's obviously true that it could be the considered decision of the development team that this interface is the best way to go given what they have to work with and, if so, one can only criticize their taste.
From my experience with angband variant developers, I don't believe this is the reason, but your point still stands.
Perhaps more importantly, it may be bad form to say "Well, they do it this way because they're not getting paid to put in the time/effort/thought to get it right, they're not consumer-oriented because the game is free, etc." or to go even further in this vein to say it's just not a professional enterprise. It's important to recognize that the people working on, say, angband put a lot of time into it and how I, say, think the current crop of developers stand up against the old guard etc. is the kind of thing people ought to shut the hell up about in public. You're right, it's not cool to talk about people's work that way.
On the other hand, in this particular case, if you look at the angband multi-window interface, I mean... C'mon. I would be interested to know why you think it's the way it is, if you think there's a good reason beyond some variant maintainer did this 15 years ago and it was marginally better in some respects than what was available in vanilla, so it was incorporated and spread to other variants and it doesn't change because no one wants to spend the time writing something better (or perhaps few or no current maintainers know what's going on in the part of the source that this is implemented in well enough to make a major change -- this kind of thing happens in angband/variants).
I guess what I'm saying is criticism of open source/free software projects ought to be tempered by the considerations you bring up. On the other hand, there's a certain threshold of shoddiness beyond which criticism is warranted and appropriate.