Golf uses a handicap system which means that, apart from elite "scratch" competitions, most participants are capable of winning competitions. I think this greatly increases the enjoyment of the sport - pitting young against old; experienced against beginners. This is great - it gives the game a friendly but real competitive edge for all. Everybody is in the same competition, with a chance of winning.
I think that we would see an increase in race participation if we could find something similar in running. I think that running competitions, away from elite races, should routinely use age-grading as a form of unbiased handicap system. OK... it wouldn't be quite the same, but it would allow young to be pitted against old... so you could keep runners really interested as they get older - and indeed, the "young greyhound" who currently feels he/she can breeze to first place in their local run, would need to pull out all the stops to win by a wide-enough margin to secure overall victory.
Beginners, or less talented runners wouldn't be able to benefit directly (I can't see how that could be practically achieved) - but even there, the older ones could work to improve their age-grade scoring... and have a realistically achievable benchmark towards which to work.
Golf usually gives prizes to the low-score and to the best handicap score. You could do something similar with running.
So many races have spreadsheeted results, which have a record of d.o.b. and finishing time, it could be calculated in an instant. The only thing is that there might need to be an investment in technology, as those races where finishing-position, rather than finishing-time, is recorded, would need to upgrade in order to monitor times for each runner. That shouldn't be too difficult or expensive with today's technology though.
A bit rambling... but in summary, running clubs and race organisers should try to level the playing field as far as possible, if we want to maintain maximum competitive interest amongst runners.. and making far more use of age-graded scores to determine the results of races, sounds like a good way to go about it.