Being "away" has never, at least since I started IM'ing in '97 ('98?) meant "the client blocks messages". It's always been a social signal, "I'm probably not here, don't expect a reply". And if people are "tempted" by seeing someone who's idle or away and feels compelled to send them a message, that's their issue, not the issue of the person who's marked as "away".
Perhaps, to me, the most annoying thing about this sort of "feature" is that it's a deliberate reduction in capabilities. Every client I use now is perfectly capable of automatically setting my status, and allowing me to set custom status states. Eliminating a feature like this from the users is akin to saying, "It's 2013, you shouldn't be saving your documents. We'll know when you're done because you'll have stopped editing it."
EDIT: Examples where custom setting away/present status is very useful to me, my phone and my laptop. My phone is connected to google talk all the time, most of the time it's marked as "away" (particularly during the work day or when I'm at events where the phone isn't appropriate). I mark my status as "available" when I'm actually able to chat, any automatic detection based on idleness would be wrong. It's similar with my laptop at home. It's on the entire time, and since I do my reading and writing at my kitchen table it's also usually within arms reach, playing some music. When I'm doing something that I want to discourage chats (but not prevent), "away" status is perfect. If I really want to prevent chat then I can go "invisible" or close it. Leaving it open versus closing it (in the case of "invisible") gives me the option of watching for other people that I might want to talk to.
Perhaps, to me, the most annoying thing about this sort of "feature" is that it's a deliberate reduction in capabilities. Every client I use now is perfectly capable of automatically setting my status, and allowing me to set custom status states. Eliminating a feature like this from the users is akin to saying, "It's 2013, you shouldn't be saving your documents. We'll know when you're done because you'll have stopped editing it."
EDIT: Examples where custom setting away/present status is very useful to me, my phone and my laptop. My phone is connected to google talk all the time, most of the time it's marked as "away" (particularly during the work day or when I'm at events where the phone isn't appropriate). I mark my status as "available" when I'm actually able to chat, any automatic detection based on idleness would be wrong. It's similar with my laptop at home. It's on the entire time, and since I do my reading and writing at my kitchen table it's also usually within arms reach, playing some music. When I'm doing something that I want to discourage chats (but not prevent), "away" status is perfect. If I really want to prevent chat then I can go "invisible" or close it. Leaving it open versus closing it (in the case of "invisible") gives me the option of watching for other people that I might want to talk to.