I use a TA for my GUF:s and occasional bookings that are not bookable online. Yes I could spend 30 mins on the phone in line and then explaining my itinerary, or I could instead spend that time working or doing something useful!

My TA has a 24hr emergency line for things like last minute changes - else there is no way I would use them.

I book 95%+ of my tickets myself, but the few percent I book through TA are always tickets that cannot be purchased online [well - not counting OTA:s as I avoid them whenever possible]. I never trust the TA to come up with suggestions for me - I just want them to book exactly what I tell them to book! They have occasionally thrown in some suggestions or spotted minor errors.