There are installations which don't support ECC, usually due to hardware limitations, but do support RSA-4k. Often this cert is the trust anchor for various other uses than just SSL, so the result is you end up using RSA-4k instead of ECC.
There's also folks who don't entirely trust ECC because it's "too new". To be fair, RSA isn't broken, and 4k is sufficiently big to be safe even with a partial break.
Actually, not just embedded systems. There's HSMs (hardware security modules) which also can't be updated to support new functions. Often this is because the underlying primitives have been implemented in fixed-function hardware to prevent timing, power and even RF analysis.
There's also folks who don't entirely trust ECC because it's "too new". To be fair, RSA isn't broken, and 4k is sufficiently big to be safe even with a partial break.