Based on experience playing with sm-players on 8mm6, I'd even guess why everything takes so long for them — on sms, the main goodies are located in treasuries, meaning not along the roads. This is where the habit of running off-road for 2-3 weeks searching for something comes from.
On the other hand, XL-template players venture off-road extremely rarely — either if there's something truly tasty there or out of desperation. The main events (movement of the hero and army) happen along the roads. Situations often arise where a conserve/hive/Dragon Utopia are ignored simply because it's inconvenient to run to them.
Essentially, most of these games went roughly like this — while the opponent spent 2-3 weeks exploring the nooks and crannies of their respawn and nearby treasuries, I scouted most of the road network, wiped out computers, cleared central treasuries (which are on the roads), and then paid a visit with an uber-army and stats. If I got wrecked, having traded units, I'd bring back no smaller army a week later (from 4-5 towns, after all), while the opponent only had +1 growth.
Accordingly, if two campers meet, the game drags on for N weeks until they polish everything clean. But if there are two aggressors, everything fits into 2-3 weeks — exploring the roads quickly leads to a combat clash.
And at least 40-50% of the template isn't used. For example, you could cut half of 8mm6 and squeeze it into L+U. It would be the same thing, just with fewer delays.
That is, the actual working space on 8mm6 is small enough that it would fit into L+U. But it's impossible to force the generator to create an L+U with a fully functional workspace using standard methods. That's why people play on XL+U, ignoring the notorious 40-50% of the map. But they are still needed — simply for the possibility of choice. If you cut the bottom part of 8mm6, you'll get a template far more pathetic than an sm.