This varies tremendously based on what you are doing. There are plenty of situations where, yeah, I'd prefer to be fully immersed in something, but there are also plenty where being able to effectively multitask is absolutely a virtue. If i weren't able to multitask I'd be working 100 hour weeks. And it's not like I really want to be fully immersed in a conference call, or preparing slides, or grinding through spreadsheets anyway.