Headphone jacks, mute buttons, and tuner out jacks, etc, are more recent frills. I've played my whole career as a bass player without any such features in any of my gigging amps. I have headphone outs on a couple of my mini practice amps for guitar, and that's it. I use an old ZOOM BFX pedal for my bass, under the headphones practicing. I once thought getting built in graphic e.q.'s and effects loops and such was the height of luxury, when they started to appear as standard features with some amp makers. Having built in crossovers, and preamp/power amp patching bays....Whoa Nelly! That's Rolls Royce style territory!
Things have come a very long way as to what many players expect to be built into their amps.