It's also the best. Without it, their processors would just be also-rans. It's the ability to run all that software that already exists that makes them more valuable than just switching to an arm chip or something else.
A 64-bit x86 computer with UEFI and wihout a CSM, for example, has no way to boot DOS or even a 32-bit OS (which could then use v86) to support the really old legacy. You'd have to resort to using a hypervisor, but considering the practical difference in performance, you could do the dumbest possible emulation and still run those 16-bit tasks just fine.
But that's just details. For the massive scale-out farms that power today's world with solutions based on OSS components, running proprietary legacy code just doesn't matter, so the backwards compatibility is irrelevant.
Like hell. Just tell all Windows users they should just replace all their software on Windows/x86 with an ARM or RISC-V box. The software will not work or will run with crap performance. They'll ditch the alternative for Intel/AMD x86. The End.
The only time they move is for something new that doesn't depend on their legacy software. Also, for stuff where they can transition unlike many enterprises locked into Windows or other x86 tech.
Or it mostly stays the same for those locked in with the current rate being billions a year for the companies that locked them in. Hard to tell how long it could be before they can get off. The IBM/COBOL crowd is still locked in after 30-40 years.
But overall, the world has changed quite a bit. We're suddenly not in a world ruled entirely by DB2, MSSQL and Oracle, running on AIX, Windows and Solaris. The software stack has opened up, and is no longer bound to any specific platform. The few big software names don't get to decide what kit to run them all...we're approaching a world where ISA won't matter. You'll buy hardware because it fits your performance and TCO targets, not because you're locked in.
What sucks for Intel is that they've failed to identify mobile devices as the "next PC", in the sense of the disruptive potential...the PC killed boutique workstations and servers and it killed them from the bottom. Along with IoT, that's two huge opportunities missed. Itanium was a pincer attempt, but no one targets the top and succeeds... you have to start at the bottom (this is btw why Power needs to scale and price down if it hopes to grow beyond its niche).
They might be in terms of getting locked-in to a proprietary vendor using proprietary language, extensions, libraries, and/or OS's that are hard to impossible to get off of. That's exactly what Wintel has been doing with enterprise software. Microsoft is still pulling in billions despite people saying other stuff would kill them for some time now. It's a combination of their market hold, lock-in, and patent suits. They're pulling $1+ billion from Android with patents despite not contributing jack to it. Oracle and SAP are still bringing in billions due to market hold and lock-in. This is a steady thing.
"What sucks for Intel is that they've failed to identify mobile devices as the "next PC", in the sense of the disruptive potential...the PC killed boutique workstations and servers and it killed them from the bottom."
That's true. That it didn't need compatibility with Intel is exactly how it killed the need for their ISA in those sectors.
"you have to start at the bottom (this is btw why Power needs to scale and price down if it hopes to grow beyond its niche)."
I agree. Great as it is, it's way too expensive. The POWER/PPC model was doing a lot better with Apple on it selling them at reasonable price. The ecosystem was better anyway with all kinds of software made for it. It had a better ROI for buyers. They need to do that again for POWER(number here) even scaling down the capabilities as the price goes down if necessary. I'd say their accelerator interconnect that can bring in stuff like FPGA's would be a winning differentiator but Intel outsmarted IBM again with the Altera acquisition. I'm expecting great things in offloading out of that if they haven't shown up already.