I've been working out for a while, but it doesn't seem that my heart is getting stronger...?

They say that athletes have a lower pulse rate. I was in athletics everyday growing up from 6 yrs old to about middle school. I was in Basketball a bit in HS and was in track the last two years. I've been going to the gym 3x a week since the summer and do about an hour of cardio while I'm there. My resting rate is 82 and has always been. My heart rate always gets to about 175-200 when I'm on the machines. It seems like my heart rate would have improved...that I would at least be at the average 70 BPM.