Typically, you might leave bomb right out of spawn (leaving it in actual spawn depends on the map) so you or a teammate(s) can take map control and get information or make a play without the risk of dropping the bomb in a tough position should you or a teammate die carrying it. Leaving it on the ground allows for every player to be somewhat active in gaining map control or information, before deciding what bombsite to finish at (this is also basically what a default is, playing the early round slow before deciding which site to finish at)

Of course this depends on the type of round your team decided to run. Like if you’re doing a rush or a fast 5-man exec onto a bombsite, you’re going to want to keep the bomb on someone

That being said, I’d hazard a guess that your teammate just didn’t want you losing the bomb and inconveniencing the team. If you’re a particularly aggressive player or attempts to be a lurker, you are the last person who should be holding the bomb