mrtd: no, no, and er, no. Your argument is full of assumptions.
Firstly, I haven't claimed anyone is "sacrificing" anything. The simplicity remains, and it will make other operatations which are not currently simple easier.
Secondly, no one said "because other platforms do it". We said "because RISC OS needs it". Which we do. There are many cases where there dependencies, and the mythical drag and drop installation doesn't apply. As Graham has said in the past, there are various programs which aren't isomorphic, !GCC being an obvious example.
If you think dependencies is the only justification, then you haven't read the article fully.
"Drag and drop installation is pretty easy". Is it? Yes, in general it is. But how do you know you have the latest version, or where to get the latest from? How you can because you have all the parts of the application? How can you be sure you have all the bits it relies upon? How do you know to change the config file if its format has changed? None of these questions can be answered reliably if done manually, and often are very frustrating even for seasoned users.
Please stop making assumptions about a system you haven't yet seen in action.
Loris: These types of installers are another reason why a system wide packager manager is good. It can be done once, and done properly, instead of ad-hoc solutions such as your example.