Hannor, imagine they send onsite staff support to repair Dell Inspiron 15 7000 or any models, but end up the parts are soldered to mb, it defeats the purpose to call for onsite repair.
Overall, it is still cheaper to replace part by part than dealing with just one-system. Makes better business sense and more savings to change the spoiled part with a good one.
Sometimes too high-end products also not so good since they make everything so thin, small and light... once a part breaks down, the entire system is rendered useless since very difficult to change and have to be brought to service center and may take many days or a week