It all has to do with the way OSPF as a link-state protocol functions as compared with EIGRP which is a distance vector protocol.
OSPF advertises a large amount of topological information about the network. Each router must learn what every metric is for every link in the OSPF area. When LSAs are exchanged, each router shares with other routers their perspective of the WHOLE network. EIGRP routers on the other hand share information about a portion of the network. So, first off, LSAs are much larger than the data exchanged by EIGRP, so a traffic regulator like the DR/BDR is necessary when there are multiple OSPF routers in the same subnet.
Secondly, and probably most importantly, OSPF creates neighbor relationships with ALL OSPF routers in its subnet whereas EIGRP creates neighbor relationships only with DIRECTLY CONNECTED EIGRP routers. So information exchange between EIGRP routers is drastically reduced as compared to OSPF.
I hope this has been helpful!