At the time it was like… wait I just bought this fancy CD-ROM… why do I need to install 30 or 40 whole megabytes to disk to play it?
At that time it was pretty common to actually install all the game files to disk (drives were slow… I think it was 4x read speed) and then the music was encoded in the cd as additional tracks of plain CD audio.
The earliest cdroms that I remember were 1x drives - so it took an hour to read that 700MB. Obviously drive speeds increased tremendously over the lifespan of cdrom (did it reach 48x?), but compared to the earliest generation it is about the same.
Sometimes you got a really bad installer, and it could take a pretty grueling 2+ hours. Some companies chose to optimize for space (thus cost..) rather than user experience.
As space got more plentiful it would sometimes be easier to copy the disk and remount it and then install.