I have seen this particular behaviour in forum software. When a feature gets popular, some forum software makes exact copies of it and add it into their feature list. Some on the other hand, possibly some open source software simply refuse to even barely imitate them. The reason is mostly " we do not do copy cat ". While it is an admirable stance sometimes it feels like being adamant or stupid to their users. Imagine a killer feature not available just because the project you love doesn't want to add it.