I don't see why everyone is so eager to give up physical media.
There are many reasons to give up physical media, not the least of which is that it is less reliable than many other forms of media. However, no one is talking about giving it up. This is talking about not having to carry it around with you all the time, for the 2 times the vast majority of the people in the world will have to access physical media. For those who do need regular access, an external will serve just fine (better actually, since Apple's Superdrives are notoriously poor quality).
I often use my DVD drive for watching DVDs, I prefer to have a hard copy as it is more reliable in the event of a hardrive crash and it protects my privacy in such a way that cloud storage never can.
An easier, cheaper, and much more reliable solution is to do a Time Machine backup. Optical media degrades quickly even without usage. But, either way, if you wanna play DVD's, get an external Drive.
Downloading software from a centralised cloud source owned by one authority, when there is no other option is simply setting up a situation where the consumer is dependant for the software supplied on the company, in this case Apple.
When did the internet become controlled by Apple? You do realize you can download software from outside the Mac App Store, right? And how is physical media better? You are restricted by retail stores which have limited space, and may simply stop selling your S/W even without malicious reasons, but simply to manage inventory better.
Therefore it seems more secure to use physical media. It also keeps control of the content in the hands of the user. I am surprised that more people do not see the dangers of cloud distribution.
Most of your arguments are terrible. The ONLY reason to use optical (not physical...HDs, and Flash drives are also physical) media is for watching DVDs, and Blu-Rays, since you cannot get DVD/Blu-Ray quality media legally online.
Another, extremely infrequent, reason would be to install large bits of S/W because your internet is too slow, or its only offered on CDs (rare).
Thats about it. All the backup, etc. reasons are empirically bad.