Old thread and all new bikes come threadless now. But the choice is still there if you buy older bikes or go custom. And there are still good reasons to go quill. Looks. Reliability. Easy (like really easy if you keep things greased) height adjust. And no need for special tools or even any degree of mechanical aptitude. Adjustments made with a common Allen key (and maybe a rock or hammer or big wrench). Yes, you can get the quill bolt too loose or too tight but the acceptable range is huge. Adjustment is quick. You can do it mid-ride or just before you leave and never sweat that you got the bolt right. Also, almost always, lining quill stems up with the front wheel is easier with the rather svelte quills than the almost always bulkier threadless. (Get it wrong and the mid-ride correction is no big deal.)
I've had one threadless bike, my first Ti Cycles. It is steel forked with 1" steerer. (I insisted on the steerer size, mostly not liking the fat headtube look.) Now? When the rather excellent Chris King headset dies, bike is going back to Ti Cycles to have the steerer cut down and threaded and the bike fitted with a Nitto Pearl or the like stem.