Interesting to know that they now keep aircraft on the tower freq until it has crossed 24R. Some years ago that was NOT the case. I remember being kept on the "ground" freq when taxiing from the hangar southwest of 24 trying to cross 24 to get to the terminal. It was so stupid. You would be waiting on a landing AC to cross in front of you so you could continue to cross the active and taxi to the gate.
By some years ago, I think you mean more than 10 years ago, before the present 06R/24L was built. As I said earlier, all active runway crossings are still done on the ground frequency EXCEPT after landing 06R/24L you will be kept on the tower frequency until across 06L/24R.
But because the landing AC was on "tower" freq and we were on "ground" freq it took a while for the tower man to OK the crossing with the "ground" man. By that time another AC would be on short final and the wait would continue. I never understood this as at other airports you would be kept on "tower" until clear of any active runway.
The reason you didn't get a crossing clearance isn't because you were on different frequencies its because there either wasn't enough space between the arrivals or there were other higher priority tasks going.
If ground doesn't give you the cross, why would you think tower would be any different? Its his call.
As an aside, AFR landed on 24L because it was the only runway available that hadn't had its ILS knocked out by lightning from the 3 hour+ thunderstorm. The length of the runway would have been more than sufficient had the aircraft landed in the touchdown zone.