As we know that some devices come with locked bootloaders like Sony, HUAWEI, hTC...If you try to unlock bootloader, the data would disappear!!!
Take hTC d826Y for example, our goal is to do physical acquisition so as to carve deleted data. But hTC D826Y is not on the support list of UFED or XRY, so there is nothing they can do. If you want to root this phone, you have to unlock bootloader first. Some may say backup all data first then root it, but how to backup "all" data is still a problem for an unrooted Android phone.
That is a very serious problem when bumping into some phone with locked bootloaders~