The perspective against competitors is a huge deal for investors. If PS4 does successfuly well this holidays, way over XB1, it's going to put a lot of pressure on MS for not being able to respond well to competition.
Part of the reasons Xbox division is even getting hounded by investors is largely due to massive competitive pressure in the more important parts of the company. Investors are scared shitless of Amazon, Google, Apple, etc, who are making huge, huge strides in huge-growth markets.
If MS had none of these pressures, no one would care that MS is making inefficient investments in Xbox, but the reality is that MS is not in a state where they can be relaxed about competitors in their major businesses.
It's no different from Google. Google is extremely dominant in search business, with no competitors coming even close to their core business that investors mostly don't give a shit when Larry Page spends money on crazy things like Google Glass and self-driving cars.
The day a 'Google Search killer' appears on the market and threatens all their ad revenue, watch investors fire shots at all these 'experiments' that are a waste of money.