why don't tubed amps have headphone jacks?

I purchased a Cary Audio SLI 80 F1 for a second system. The main reason was it has a really nice headphone section and jack.

Pawlowski, cool. That said, I had intended to mean nothing more than you wouldn't want to drive cans off of speaker taps (or the final amplification bits of an amplifier intended to make speakers go). Can't imagine that cans on 250 + watts would fair so well. Thus, however you get it done, I presume you'd need more than what you find in a vanilla speaker amplifier. But, clearly, I know just boatloads about "electic bits...."

Keep in mind that cans are usually 32ohm, so the amp would 'see' much less of a load, putting out approximately 1/4 of the power as it would into an 8ohm speaker.

Normal listening levels for a 90db/meter speaker requires only a few watts, if you quarter that, you really aren't putting much into a set of cans with the volume knob at the same level.

My McIntosh 2505 has a headphone jack.

Trucker/Mezmo; one of my favorite pair of headphones was the AKG K1000. It didn't even have the normal 1/4" headphone jack. It connected directly to the speaker terminals. People have driven them with all type of amps!