Pipelining pisses off owners of servers and busy websites, as the performance gain is alot more minimal than you think for the client, while it's a whole lot more load for the server. Alot of server owners who know what they're doing use counter measures to make their servers ignore pipelined requests (only one request at a time will be graced with a response), while some will go further and make things slower than even just using one connection for pipeliners.
I basically don't care right now, my own server is underused alot and it's load has never gone above even 0.1, so i forget about it.
But yeah, some builds of apache have pipelining disabled by default. Especially windows builds, seeing as on windows apache will open a seperate process for each connection (you have 7 people connected to your site, you'll have 8 apache.exes (7 hosts plus 1 master) running.