Here's my take on the rifle. Is it better to have? Absolutely. It gives you options. Is it the best idea to deploy it? In most cases, no. You're not walking around with it on, so accessing it is going to take time. Time probably best spent unassing the area and calling in reinforcements. If you're caught where you need to engage the shooter, it's going to be on demand and right then. How far away is that rifle in the trunk likely to be? By the time you access it, is it likely that 1st responders will see you instead of the active shooter, placing you at greater risk from responders than the shooter? These are things to consider.
One caveat is those who frequent remote areas. A 1st responder may be 40 minutes away instead of 4. I'd definitely be adding a rifle to the kit under those circumstances, as the range to the shooter might be longer as well.
Yep, I think my original statement was from a LEO source where they may be engaged in an active shooter for a period of time, so they need to get to their rifle.
I always remember watching the Shooting in the tower in Austin Tx where the LEO put out a request on TV for deer hunters to bring in their rifles, as they couldn't reach the shooter effectively with their pistols. Revo's at the time if I remember right.
I travel with my rifle a lot, as the farm is 45 miles from the home. Lots of "varmints" at the farm.