Why so much cynicism? The people working there genuinely care about this stuff. Maybe you disagree with technical decisions but why start by projecting your fantasies about their motivations?

RSS is OK for what it does, but it isn't realtime, isn't signed, and doesn't support arbitrary structured data. Whereas AT is signed, works with any application-defined data structures, and lets you aggregate over millions of users in real time with subsecond end-to-end latency.