That and the fact he was considered to have 'gone native' at the time - which was frowned upon by the PTB.
It wasnt so much that they just dismissed it, there was a fair chunk of 'thats not what we want to happen' mixed in there too. The British had promised so many people ownership of the same bits of land that by the end of the war they didnt know whether they were coming or going - sadly thats the way it has stayed ever since out that way.
I love history, but one of the things I dont like so much about it is that generally the devious/nasty/generally unpleasant get away with it and leave innocents to pick up the pieces (or in the case of the middle east - be the pieces)
With the Ottoman Turks having sided with the Kaiser during WW1 I'm sure the British realized the strategic value the oil reserves in the mid east would have to Germany. And since the Turks were the overlords of that area we call the mid east today, defeating their influance there would be imparitive for future British security. Certainly it would have made things quite different for the Germans by the time of WW2 as the Fascist saw piecetime only as a time of preparing for the next wars.
For Lawrences part, he wasn't thinking about the next world war I'm sure. None the less his unconventional Gorrila warfare was likely one of many desperate acts in that time to broker the necessary outcome at any cost. The high command would have had more insight to the outcome that was needed even if promising spoils was their only avenue to those ends.
In a book by Steve Shagan titled, "The Formula" published in 1979 (fictional but based on obsucre facts regarding German Synthetic Fuel production from Coal during WW2) a reader can see why the efforts of those like Lawrence were so critical. It served to stop the Germans access to mid east oil while forcing them to expend their coal resources. Incredably the Germans were able to wage war by the late thirties and into the fourties with inconsistant crude oil supplies. Polesti in Rumania being one primary source. Synthetic fuel, oil, and heavy lubricantsl, etc produced from German Antricite allowed their war machine to be as formable as it was. Imagine the course of history had they secured the mid eastern oil supplies during WW1 ?
Shagan quotes Thomas Jefferson in the opening of "The Formula" citing
"Money, not Morality is the principle commerce of civilized nations".
That may hold the key to why the devious/nasty/generally unpleasant prevail
and the innocents pick up the pieces or become such.
"The Formula" was largely researched in Germany at the United States Mission, Berlin Documentation Center.