Whilst i agree with the comments of two previous post the fact remains we have what we have in terms of passengers and i think its more to do with the frequency and therefore complacency of regular flyers.
Evacuations should be a absolute last resort, the BLK Jet2 evacuations was i understand order by fire 1, so no real choice for the Capt, The GLA Jet2 evacuation would appear* to be due to misting following ingesting deicing fluid either from the runway or following deicing, something that might reasonably have been expected and therefore briefed for the cabin crew.
I await the report on the EMA Jet2 evacuation, but the AAIB are looking at the R1 relay issue according to early reports an issue that would explain loss of cabin PA and other issues reported.
Prior to considering an evacuation the Capt should always ask 'Cabin crew report' I can see smoke, what colour is it?, its white, is it clearing? how far can you see?
Evacuations in most case will result in injury!! A well handled event was the the aircraft (not Jet2) that left R14 at LBA some years back and ended up with the port side dangling over the drop, an evacuation there would have been a theme park slide almost vertical