As someone with a role that touches global teams in a lot of different places, I can identify wanting to keep people together for certain things.
Yes, there are some really wonderful collaboration tools and methodologies for scaling agile etc, but having lived in this world with a multiplicity of distributed development teams, functions, PMs - you name it I really do recognize that with all those tools its a trade-off - and a lot depends on what you are doing.
As a quick thought experiment - let's say there are three of us in a global and we are given some work to do. We each have a computer, and we're operating to German employment legislation(because it's funny*). The worker's council said we can only work eight hours a day, and only get one hour a day overtime out of our core hours. Because I'm pushing it to the extreme none of our working days' overlap(someone may have live on a boat as a nomadic denizen of the seas). The work is highly collaborative, and we'll be using scrum for a weeklong sprint to produce the work. The fate of the company rests on us delivering the thing in that week.
Now, you have an option to fly your team to the same location(In the TARDIS, 'cos your travel budget is boss). With some much riding on this week do you take it?
For pretty much all tasks there is a tax to pay for not being co-located - I think it can be mitigated, but the most effective globally distributed teams I know recognize there is a performance and work life hit to this that is non-trivial. All these remote collaboration tools are compromises at best.
*Actually Geman employment protections/work culture are probably the best I've seen.
