I still tie leaders but mainly specialty leaders for nymph fishing. For dry fly fishing, I use a AirFlo poly leader. For streamers, I use a stout, short, commercial leader. For nymphs, I use hand tied leaders with short butt section, bright mono sighter and long, light tippet.

IMO, tying leaders is very helpful in learning about leader design and materials. This knowledge is helpful in purchasing and customizing leaders.