1) Each gmail user is also a GTalk user. It's very convenient to be able to reach people not using any other IMs through the GTalk's web interface.
2) In corporate environment it's sometimes the only option, due to inability to install 3rd party software.
3) There's a huge advantage of GTalk over Skype - Skype is a P2P protocol. If you send a message to an offline contact and disconnect, he will never receive it unless at some point you are both online. It makes sense for VOIP obviously, but for IM that's just ridiculous.
For the same reason there's no server-side history - no way to reach lot of important information after you reinstall the system, break computer etc.
2) In corporate environment it's sometimes the only option, due to inability to install 3rd party software.
3) There's a huge advantage of GTalk over Skype - Skype is a P2P protocol. If you send a message to an offline contact and disconnect, he will never receive it unless at some point you are both online. It makes sense for VOIP obviously, but for IM that's just ridiculous.
For the same reason there's no server-side history - no way to reach lot of important information after you reinstall the system, break computer etc.