I'd agree if you talk about "most projects". But here we're talking about a platform - you can't fault Microsoft for caring about performance! .NET is absolutely not meant only for small sites, my current employer is heavily invested in .NET and we'd probably be dead (performance-wise) without async. Definitely couldn't run our services with PHP (not without Facebook-like investments), we already outgrew that kind of traffic.
I'd be willing to bet more projects have been killed by trying to architecture for performance up front than have been killed by being too successful for their own good and keeling over.
If Twitter could make it past the Fail Whale days, I think most of us can too.