why do cd's give a more accurate reproduction of the orignal sound than cassette tapes?

Answer 1

Laser burn onto a fixed media instead of a magnetic transfer onto a flexible tape.

CD player is a much better "reading" tool of the media than the playback head of a tape player as well

Answer 2

cassettes tapes record analog signal on a tape.
The tape suffers from various problems:

The tape can be slightly elastic, and the drive speed is not perfect so the speed at which the music is recorded and that at which it is played can vary a little.

because the tape recording is magnetic and it's spooled, there can be a effect of copy from one piece of tape to the next that is spooled close to it.this is more noticeable in the silences, if you have left your tape to the sun.

if the recording signal is too strong, the signal is more than the tape can record and it sould saturated.

There are probably other effects like separation between left and right, etc.

A CD is recorded digitally as data on a disc.
The data is time coded is 1/75 of a second if i remember right, so you the speed at which it's recorded and played is much more stable.
also it will sound better because if there is a damage to the cd the player has a mechanism to replace the missing data with spare data or with faked data : there is a little bit of redundancy so if some data is missing you can reconstitute it and if not you create it from what's before and after and the listener will never know it.

Because the recording is digital it's more precise for very detailed sounds.
However some people do believe that analog signal is better (digital signal means you have only have a finite number of values to represent a voltage whilst analog is not limited in that fashion)

Some people think CD is not good enough and Super Audio CD which is similar to a DVD with only music.
It's probably overkill unless you have too much money.