This is done primarily to preserve system performance issues. Multiple nested/complex data/segments and criteria increase system load and degrade performance of your (and others) surveys.
Not really. This is a system imposed limitation and we are unlikely to change this.
Currently you can have maximum 10 groups at a time. If you need more Groups you can delete the Groups that are not required and create new Groups. Deleting the Groups does not affect the data in any way.
This feature is available with the following licenses :