Some of the legacy projects I've worked on would have a hard time supporting 64bit x86, never mind an architecture that changes the endienness. Yeah, yeah... you can say what you like - this software was written in the 90s for DOS and went through various 'upgrades' to get it working on Windows. People were 100% confident that the code would only ever have to compile for an x86 machine, so they simply didn't worry about it - even if they were aware that things like byte order or number of registers are not guaranteed. At this point the only sensible solution is to bin it and start again, but that's hard to sell to the management and customers in terms of cost and lead time.
Conversely, open source has a great history of supporting multiple architectures - that's why there is a complete software stack for ARM (and MIPS and PowerPC and...) more or less as soon as the hardware products hit the shelves.
tl;dr Yes, there are plenty of old but never the less very useful and actively used Windows applications that can't simply be recompiled for ARM.