The bottom line, some people are fully aware of what they are doing and just want to use a receive address they used before. This is an obvious advanced bitcoin client here, please don't turn around and say you are looking out for the new bitcoin users and their practices. If I want to use another address, I'll pick one. I can see the very paranoid, overly security conscious people worried about this, but their also the ones that won't even use online banking because they're afraid their account will get hacked. Being overly paranoid and secretive puts you into certain positions you have to deal with, and if you are hiding something that's a whole new story.
This isn't a conspiracy theory. No one is stopping you from reusing addresses. But it's not the default behavior because the privacy implications are egregious. It absolutely
is our job to set sane defaults, and users that know what they're doing can deviate from it.
This topic has been discussed endlessly, everywhere. It's generally accepted best practice that you don't reuse addresses
unless you have an explicit reason to. It is discouraged, but there are reasons to do it (such as donation addresses).
There's a reason every Bitcoin client is moving towards BIP 32 -- so they can employ best practices without the issues with backups. If you don't like it, then go ahead and reuse your addresses.