Actually, the very original PCMCIA memory cards were descended from micro-card ATA memory cards with the pins and form factor that later became PCMCIA. When PCMCIA became a standard (and later became "PC Card", which evolved into "CardBus",) they kept the old ATA compatibility.
And Compact Flash cards are just reduced-size PCMCIA flash cards. And thus, retain 100% ATA compatibility.
That's why a Compact Flash-to-IDE converter is just a simple wire converter, with no active controller chip.