It helps if you do frequent backups and if you have your important data on a separate partition. However, the majority of users do not do either of those things, and if the MBR and backup are erased and you have multiple partitions on the main drive, recovery will be problematical if you do not know where the partition breaks were in the original configuration.
For instance, on this machine the important data is on sda3 but on other machines it can be on hda5 or sda6, depending.
Most users treat their PC like an appliance: turn it on, read and send emails, view certain websites. Reconfiguring or reconstructing their machines is not in the cards.
Then compound the fustercluck with an encrypted disk.