Ask HN: Why don't more software projects use BitTorrent for downloads?

It seems like it would be great for open source projects with limited funding to use BitTorrent for downloads. However I only see a handful of projects using this model, e.g. LibreOffice and GIMP. Whereas a lot of Linux-based OSes just host their disk images over HTTP, which I imagine could incur substantial hosting costs over time.

Why don't more software projects do this? Are there any big downsides to distributing torrents as opposed to traditional FTP/HTTP downloads?