I have an Acer netbook and a Chromebook, neither with an optical drive. Several years ago, I bought a cheap ($40) portable optical drive, which I use to burn Linux image backups from the netbook. This external drive works perfectly with the Macbook for things like watching movies. Other than that, I have no need to use an optical drive with any regularity, and I far prefer the lighter/thinner package that results from omitting one.
The idea behind the MacAir is to learn how to use iCloud drives for your big files. Nowadays you don't need to install the complete software, as many of them can be downloaded from the internet or rented for a certain period of time. Ask yourself how many software you have installed and never used. MacAir is to carry the basics... I do so...
While I almost never use a cd/dvd drive I had the same concern as you. In the end I decided to just buy an external drive that I keep at home (although it is light and small enough to carry with me). Buy the Macbook and if you find that need a cd/dvd drive you can get one for really cheap both from apple and 3rd party companies. But to be quite frank I doubt you will because everything is now streamed from the internet.
I do not usually end up using CD/DVD drive so I am OK with that being absent. Also you can always buy a USB CD/DVD drive. That is atleast my plan, as my driving need to buy was a light weight easy to carry laptop.