I don't think this question can be improved into being a good fit for Stack Exchange sites in general. It is, of course, both reasonable and answerable, but that is not enough. All you ask is a reason, and someone has provided a reason. You still haven't accepted it. This indicates to me that what you want is to speculate on possible reasons (of which there can be many) - a very broad question.
Secondly, I don't see how this is an Ubuntu problem. MS doesn't provide 64-bit binaries for any Linux distribution, therefore the problem, if it exists, is squarely on the Microsoft side.
Thirdly, any possible reason there can be, boils down to an opinion. It can be one person's opinion that some factor is good enough to be a reason and it can be another's that it isn't. You're asking for an opinion poll.
This question is off-topic thrice over for me.