Password protection will protect personal files, and is adequate, but protection increases with how well it is implemented. If you merely set a login password for the OS, this will prevent casual thieves from logging on to the system and taking your files once they have the device in their possession but it will not help against thieves that know enough to open the machine and remove the hard drive and attach it to another computer. With proper full disk encryption and a long enough passphrase even sophisticated hackers will not be able to retrieve your personal files due to the strength of the cipher.
If you have everything password protected on your computer--and this means passwords that are a mixture of numbers and letters and more than 8 characters--this does protect your personal files against a potential robbery. This is the best way to keep it protected, except for maybe a safe deposit box.
Yes, I think that password protection of computers does an adequate job in protecting personal files in the event of computer theft during a robbery, because a computer is very hard to hack if you don't know the password. Most people who steal computers are not smart enough to know how to hack them without password knowledge.
In a situation such as a robbery, the perpetrators are interested in money -- not information. The password protection on a computer is simple yet effective in deterring them from accessing the information. But that potential physical theft is why actual information should be stored behind passwords online, in the cloud.
I do not believe password protection of computers does an adequate job in protecting personal files in the event of computer thefts during a robbery. My current laptop offers no real password protection and when I had my Mac, I didn't feel it was adequate either. I'll be glad when the add the kill switches.