This quote is related to FireFox and Apple, but it's the same idea:

�Apple releases new versions of its operating systems relatively quickly, and each new version contains
significant changes that we must adapt to,� Aas said. �This requires resources, and with limited resources
this sometimes means we have to make tough decisions about where to invest.�

http://www.macworld.com/article/1168241/mozilla_sets_end_of_firefox_for_os_x_leopard.html

Mozilla had "limited" resources (revenue, but revenue is resource in software) of over 163 million USD in 2011� 

Marcus