What is appearing to me is a cold, harsh reality that companies have really no interest in supporting anything, unless it means ongoing revenue streams for them.  For them, the used game market is of ZERO interest.  Included in this is the very likelihood that Sega doesn't really care about the old carts about, or heck, even Nintendo.  In light of this, why would they care about supporting backwards compatibility, if they can't make money from the sale of content in the past?  Sure, the backwards compatibility provides a way to have a good library for your system out of the game.  But, financially, if you own the games, why are the companies motivated to continue backwards compatibility support, outside of not ticking off their base?  Eventually you sees stuff with Nintendo and their portable platform, where they quietly phase out compatibiility to older stuff on their handhelds.  Like, the DSi did away with the GBA compatibility, and so on.

Ok, so the reality is that companies then don't have a drive to support backwards compatibility, so they want to phase it out.  So, this then means that, if aligned as companies want, you can't play your old stuff.  It eventually will expire.  So, in light of this, if you can't play your old stuff, what is the point of backwards compatibility?

So, can someone explain what the point of backwards compatibility is in the end, if you eventually can't play your old content?  And companies don't benefit from ti at all?

Because when my GC broke I kept my best games and can play them on my Wii?

I'm more of a glass half full kind of guy.

That is benefits of it.  What I was talking about is the reasoning behind it.  It is not in the financial interests of companies to support this long term.  As it is now, they want you to rebuy stuff you had in new formats.  I believe, for example, that the Wii model now is phasing out Gamecube compatibility.  Once Nintendo made its money, it isn't motivated to have you keep it.  They want you to rebuy the HD versions, for example.  Look at what they did with Pikmin and Mario Tennis on the Wii, for example.

didn't realize the DSi removed my DS lite's BC capabilities..

It's too early to criticize PS4.

All glasses are always full. It is just a matter of whether they are full of liquid or air.

Backwards compatibility helps to encourage brand loyalty. If you own 50 games from console Y than can be played on new console X but not new console Z, and both console X and console Z are very similar in all other respects, which will you buy?

Backwards compatibility becomes less important depending on how new consoles differentiate from each other via other means (notable exclusive titles or other exclusive features/services), and depending on whether new consoles are able to retain consumers through other features that carry over from one platform to the next (Trophies/Achievements, etc.).

Same thing happens with mobile phones. People bought iPhones when they first came out, and the amount of purchases made through the App store encourage a certain level of consumer loyalty. Some still transition from iPhone to Android and vice versus after heavily investing in one platform or the other, but it's less common than it would be if such investments had never been made.

Edit:

This guy is a pretty classic example:

Prominent Xbox features are enticing him to buy the next Xbox.  Now, achievements alone would probably encourage him to stick with MIcrosoft going into next gen, assuming their prospective line up even remotely matches what he has come to expect from an Xbox console, but let's take it to an extreme and imagine a scenario in which Microsoft decided to forgo the Halo franchise in favor of new IPs (lol).  Legacy support for Halo Reach and 4 and their online communities would provide him with an incentive to buy a new Xbox over a new PlayStation in leiu of a completely new Halo.

I think they have an interest vis-a-vis games on demand / classic games. Backwards compatability should be an offshoot of such technology.

After all, publishers are wanting more long-tail revenue for historical games. If someone like Square Enix can keep selling thousands of copies of FFVII every month on the PS3, then they have a marked interest to ensure the titles are at least available in some fashion. Given the fact that the data is still the same, I don't see why the disc is a huge issue.