Why to: Running a Tox Bootstrap Node helps some new users join the Tox network and start communicating. This helps Tox be more reliable and reach more people, and helps the Tox project in general.
Why to: Understanding the pros and cons of different ways of sharing Chat IDs in general is pretty important as it can be a factor in how you authenticate that the person you are talking to is actually who you are talking to. Additionally, Tox provides several means of making it easier to share the long, secure IDs necessary to run Tox.
Howto forthcoming, for now see Compiling Toxcore.
Why not to: Tox is still in development, and major changes to the code might have an effect on whether clients are compatible with each other. Many people receive daily or near-daily updates. If you're only interested in using a Tox Client to communicate and don't have an exceptional need, it's probably best to get it via an official channel, either the developer's website, or an official package or source repository.
Why to: Sometimes, official builds might become inaccessible for one reason or another. Even the source code may become difficult to obtain, if say, an oppressive regime were to attempt to censor this web site by preventing it's users from accessing it. But as John Gilmour said, “The net interprets censorship as damage and routes around it.” Community builds could remain accessible at different domains, be hosted on hidden services or distributed on other censorship-resistant channels.
These How Tos link to external resources.
Why to: Tox GroupBots are able to automatically invite users to group chats, allowing for groups of people to connect and communicate using the GroupBot to host the chat without necessarily pre-sharing their Tox IDs. Essentially, it makes it possible to meet strangers through Tox. It's educational? Because you might feel like it? For fun?