Blame the US for its puppet dictatorships that generated fierce opposition, usually in the shape of religious fundamentalism. Iran was not Wonderland under the Shah's regime. The West and the US want almost no country in the Middle East to be prosperous and powerful, under whatever regime.Many countries who doesn't use Latin alphabet do use English signs, including all Arab countries except Lybia.
Iran has many different languages:
Anyway, I was thinking about when, in the 60s and 70s, Europeans used to drive or hitchkike along the "Hippy Trail" all the way from Europe to India and Nepal, crossing Yugoslavia, Greece, Turkey, Iran, Afghanistan and Pakistan. It was all quiet and peaceful, different countries, people, languages, cultures and religions but nobody risked their life to travel across that part of the world. Then came the Iranian revolution, the Soviet invasion of Afghanistan, the Taliban terror in Afghanistan and Pakistan, the US invasion of Afghanistan. Obviously going that way overland is no longer feasible. If the Western world did a lot of improvements in the last 50 years, in those countries happened the countrary. Imagine how these places were, plenty of youngster with long hair and colorful dresses, smoking, drinking, playing the guitar, and driving around with hand-painted VW vans. Now: military installations, derelict buildings, women with burqa and men with kalashnikov.
Iran today could have a lot of touristic potential if it hadn't that crazy theocratic, women-murderer and terrorism-sponsor dictatorship. They have history and beautiful landscapes. The same can be said about Saudi Arabia, that is plenty of oil money to develop tourism.