Both the A330 and the A343 burn approx 6T/hr.
Obviously losing an engine an engine on the A330 loses you 50% of your thrust, whilst of the A343 you only lose 25%.
At 230T an A330 will drift down to approx FL200.
At 230T a A343 will drift down to approx FL290.
(*At LRC)
The A343 can carry 33T more fuel than the A330 too. (ie: an extra 5hrs)
Figs quoted abv are rules of thumb only; more accurate info is in the FCOM. The MTOW of a heavy weight A330 is 233T, whilst a A343 is 275T.
Lastly, many routes that are now ETOPS, werent ETOPS 15yrs ago. The enroute airports werent suitable, didnt have navaids or were communist. (The polar route is one.....plus USSR, Eastern Europe China, Iran were hardly our friends).
There is less of a requirement for 'light' 4-engined aircraft nowadays...but as Dan explains above, it is still there.