It makes some attacks a lot easier. You usually need admin access to install a rootkit so your virus can re-install itself. You also get full control over the

It makes some attacks a lot easier. You usually need admin access to install a rootkit so your virus can re-install itself. You also get full control over the network stack, which makes it trivial to MitM traffic. Admin access will let you disable whatever security monitoring tools are installed so you can stay undetected for longer. Locking down admin access is less about protecting the local machine and more about preventing the laptop from becoming a jumping off point into more important pieces of infrastructure. It's by no means fool proof, but it adds another security feature that has to be countered. I don't know whether it's worth the trouble it creates, but I don't think it's totally without justification.