I think the community needs to get smarter about attacking objectives (which, at the moment, most players don't really seem to have a good grasp on). At the end of the day, Siege is about defending/securing the objective, not necessarily about killing everyone on the map; if people decide they want to lurk, all the attackers have to do is breach into the objective room directly and start securing it. Most people think they have to go hunting down defenders who lurk, which usually results in them getting killed, which then results in them getting frustrated over it. Defenders SHOULD have the advantage of lurking throughout the building(s) because they are the ones setting up traps, setting up ambushes, and watching cameras. What people don't realize is that if you move into the objective quickly when only a few people are defending it, anybody lurking has a severe disadvantage moving back into the objective room from their far away hide spot. For an intelligent attacking team, it's like shooting headless chickens, really.

Simply put, defending is a much easier concept for people to understand since it (at its basic level) involves holding down a few rooms and killing anyone who moves in on you. Pretty easy. Attacking takes a greater level of thinking because you have to dissect the whole building, find traps, find kill holes, find defenders and where they are positioned, etc.

I've noticed that most people nowadays check windows almost every time they spawn to avoid getting spawn peeked (unlike it was a few months ago, where people would completely ignore them). I think the Attackers are just behind on the "community learning curve" compared to Defenders. It may take some game balancing to even this out but I think it will become more even over time just naturally.