Yet another point to add.
I don't think anyone will argue that a pilot CANNOT perform a preflight given adequate training, but the fact is that, in Australia, pilots AREN'T given adequate training on preflights. This is evidenced by the number of times I have been asked by a pilot what the limits are on simple things like tyre and brake wear. If they had decent training, they wouldn't need to ask. I'm not saying that pilots shouldn't ask an engineer if they have a legitimate query, and I'm more than willing to help them out when they do, but simple things like tyres and brakes should be known.
Quite a few people have mentioned about practices in Europe, with pilots doing all preflights. Having spoken to a number of pilots from that part of the world, I know they are given a course on basic maintenance BEFORE they are able to perform a preflight. This course goes for something like 3 weeks. How much maintenance training do Australian pilots get?
Then there's the matter of time. Pilots don't get to start their preflight until all the passengers have disembarked, which can be 10 minutes after arrival. This doesn't leave much time to carry out a decent walk around with a 30 minute turn around, when they also have to attend to the rest of their cockpit duties. No wonder CASA notices them taking short cuts...they don't have much choice.
I guess it all comes down to common sense. Pilots have neither the time nor the training to carry out a decent preflight...engineers, however, have both. This, of course, can be rectified by giving pilots maintenance training and extending turn around times, but why bother? Engineers are there already, why not use them? But then again...the peolple who make these kinds of decisions could never be accused of having common sense, could they?
BTW...I am NOT having a go at pilots, I AM having a go at the bean counters and decision makers.