I've often wondered why the mainstream UK-based Christian sects actually bother with evangelising in this day and age.
They do it because it's the Church's only raison d'etre, Gordon.
They would be much better letting good deeds do the talking, which are much more effective than spouting dogma, imo.
It's not so much good deeds - what on earth are those anyway - but how people live in general that is effective. 'Let your life be your message'.
I have found that on the occasions I have really managed to get in tune with God, my actions/behaviour have stood out from that of others and I have been asked what it is that is making me do that. That is as much evangelism as the subsequent explanation of my faith - a combination that has more often than not drawn those I'm associating with at the time to ask further questions about God and what he can do for the individual(s) asking the questions.
It is interesting that the way Jesus worked was by using a miracle or telling a parable and then drawing a teaching point from it.
To pop back to Gordon's original question about why Christians bother doing evangelism, evangelism isn't simply talking to people - and never has been.
The comment - "Go out and preach the gospel, only using words where necessary" - has long been attributed to St Francis of Assisi. At the churches I've been associated with, the majority prefer to use the former rather than the latter - at least initially.