Though Leeds have been a big club since the mid 60s, they weren't before then. so they don't get anywhere near the history of more traditional big clubs like the old 'Big 5' of Utd Spurs Pool Everton Arsenal
For example we'd won the FA Cup five times and 8 major trophies altogether before they won their first trophy in 68, IIRC.
Leeds had a great 30 years but they're nowhere the level of the 5 already mentioned in winning trophies over many years.
http://www.krysstal.com/trophies.html
Sheffield Wednesday have won more trophies than them.
People like me who remember the pre-Revie Leeds when they were anonymous place fillers in the lower leagues won't be that surprised they are so low in the trophy table. Others may be.