The search for “security” is just started. Whether is makes sense or not i let you choose. Your point stands, but laptops have usually “unlocked” boootloaders and so it would not make sense as in a phone.
You need vendor locked in devices to achieve true security (and lose your freedom of course)
(Just a bit more clarification. A truly secure and locked device takes your freedom to modify and really own the device. It would be only a matter of time you will be renting your own device)