I have a netbook, and like all netbooks, it does not have an optical drive. Is it a problem? Not really if you take suitable precautions i.e don't rely on a backup/recovery on the hdd. I made an image and keep that on an external hdd, likewise folder backups.
As regards installation issues, you are quite right, it does present problems so you really need to factor into the package an external dvd writer if you are thinking of buying one.
take up space, add weight, consume a lot of power and are rarely used in normal day to day tasks. Also solid state hard drives will become the norm in a lot of machines to give the user a lighter unit with a longer battery life.
Installations and games can be installed via lan, usb, flash drives or external optical drives. Patches for games will make them run without inserting a cd to kick start them. Recovery partitions will install the operating system without the aid of the O?S cd.