Yep, I log my dives. I find I write more when I am traveling and diving off island. Mainly I log dives because its a CYA...if I am teaching, I log the student and the skills covered. If its a fun dive, I log the ppl I take out. Also log any exciting events such as accidently swimming thru a giant trigger fish's breeding grounds, and any subsequent bodily damage that might have occured to me. I dont log pool training dives unless I hit more than 50 min underwater.
When I dive in Saipan, I use compact 60's with a skin, so when I travel, its helpful to know how much wt I use in my full wetsuit, as I dont use it often, plus most places use standard tanks. The logs also come in handy to brief customers on dives to islands nearby that we take by boat. I find that as I increase in age, sometimes my memory decreases. Damn the old age!
As with some ppl who have posted, I agree, a log shows proof of ur experience in diving. I have been asked several times that I show my log. I just returned from Bali and despite showing my MSDT card, they still asked when was the last time I dove.
Keep Logging and keep diving....