However, if one is to accept the notion that a backup hard drive with a cloned OS on it is an acceptable substitute for install media, one must accept the notion that it is necessary to walk out of the store when one first purchases a computer with an additional hard drive.
The need for a backup hard drive has nothing to do with install media. Whether you get install media or not, you still need a hard drive (or two) for backup.
Apple makes and sells great computers, but they're not the best place to buy hard drives. Get your drives (and any RAM beyond the bare minimum) elsewhere. I wouldn't walk out of the store with either.
And making a computer unable to boot if the hard drive fails is also not reasonable.
But it does boot after the hard drive fails (and is replaced). If you have a slow internet connection, it boots really really slowly, but it does boot.
If you choose to have only a dial-up connection, you have to accept that you have a slow connection. Everything runs slow, not just the first boot after replacing the hard drive.
Note that I'm not saying having only dial-up is a wrong decision. I can conceive of many justifications, ranging from budget to availability. I'm just saying that it has consequences. Unavoidable consequences. Even the very best of reasons for having only dial-up won't make it fast.
Apple does what they can to mitigate the problem by offering the use of their in-store bandwidth. If the store is too far away, you're free to look for alternatives that are closer to hand. Or you can dial up, start the download, and check back in the morning.
There are services that provide guaranteed up-time. Web hosting services, especially for business web sites that include an on-line store, often guarantee an upper limit on downtime (both as a percentage over the year, and per-incident). Those services come with a hefty premium. Apple's not in that business. They sell you a computer. Contingency plans for what you'll do if it goes down are your responsibility.
If instead of a disk, it's the screen or power supply or mother board that goes down, Apple will repair the computer under warranty. Heck, they'll replace the disk under warranty, and even take care of re-installing the OS. (They won't replace your data. Backup is your responsibility.) But you're looking at a trip to the store to get any repair work done. It may be FedEx that makes the trip, but Apple is not going to ship you the spare parts and tools to do it yourself. They also aren't going to bundle the tools and spare parts with the computer, to be used just in case the computer breaks.
Think of the install media as a tool that you can, if you're so inclined, use as part of an in-house disk-replacement procedure. It's a tool that makes the procedure faster and more convenient, but it's not essential. It's a tool you can make on your own, or buy from Apple.
But Apple isn't required to give you every tool and part you might need. Your computer no longer comes with USB and FireWire cables, and has never come with a ThunderBolt cable. Apple used to include a blank CD-R (and later a DVD-RW) with their computers; they don't do that any more either. My first iPod came with a very nice carrying case. They don't do that any more, either. So now Apple has added installation media to the list of freebies that are no longer thrown into the box.
Why not include installation media? What's the compelling argument against it?
They cost money, and for most users do absolutely no good. The software comes pre-installed, so most users never use them even once before filing them in some forgotten corner where they'll never be found again. Even if it only cost a penny (and it'll cost a lot more than that for the packaging alone), it's wasted money.
It also looks bad. Apple prides themselves on their packaging. No extra styrofoam, no extra cardboard, no extra plastic. And now no never-to-be-used DVDs.
