Why isn't DT that big ?
In your opinion why did DT never get world famously big, as in sold out world stadium tour big with the likes of GN'R, Metallica and Maiden ? Sure they are famous among the rock/prog group but they never really passed that barrier, ask any country/pop teen about comes as you are, sweet child of mine, nothing else matters... they might not know specifics but they've heard it before and at least know the band's name.
Now one might say, well DT has music that is not for all ears, too many time signature changes, too heavy, too unconventional, songs too long ... etc. But they do have tome stuff that is commercial and short enough to be played on radios and catchy enough to have kids singing along their chorus ( see This is the life, Along for the ride, wither, then bigger picture). They Have political/religious/easy lyrics, complicated... They have an iconic guitar hero, they have it all.
So, If the problem is not lack of material for everyone, and they have something that fits every kind of taste, why the hell are they not up there at that god level status with all the greats ? Failed marketing strategies ? Lack of commercial/radio/internet/tv Ads? Poor SEO ?
What are they missing to be at the ultimate level ?
Edit: Not being big says nothing about their quality, influence, and importance in the music world.