Locking laptop startup (boot) is a first line of defense against unwanted access to your machine. Most laptops have a BIOS management console to set a boot / startup password. On old laptops boot passwords could be easily removed by taking out the clock battery. Modern laptops require a more sophisticated method to remove a boot password. In any case if you set a startup boot password, don't forget it!
A startup / boot password does not prevent access to the harddisk unless it's protected with software like SafeBoot (McAfee) or equivalent functionality. Removing the harddisk from a laptop and accessing it using an SATA/PATA USB interface is quite easy. To protect the disk from being read is whole different story and has not much to do with laptop startup locks.
In any case the laptop industry has become more advanced and also have introduced finger print locks. Very innovative but for traveling maybe a bit too fragile technology. Being locked out because those weary sweaty dusty fingers are not recognized is a bit annoying.