Why are PS4 and PS5 unable to read PS1 or PS2 discs?

Question

They are clearly able to emulate the games based on the PS1 and PS2 games being available on the digital storefront.

Edit: Thank you all for the informative replies.

In: Technology

Answer 1

CD, DVD and BluRay all use different lasers with different wavelengths. A lot of commercial players like the ones you get for computers or media players does come with multiple lasers that can read all disk formats. However PlayStation have chosen to save some cost by only including one laser. There are also some other differences in the tracking mechanism which makes them incompatible. They used the tracking of the grove in the CD to prevent illegal copying of the disks but this made the hardware a bit more complicated which they did not add to the later DVD and BluRay players in the later versions.