Part of the problem is, these two things are working at cross purposes. Contrary to your instinct, making a language easy to learn will also probably harm the cause of fostering interest.
The problem is, from a sort of detached, scientific, logical point of view, it sounds like a great idea to have a language that is simple, easy to learn, containing definite rules, with no irregularity, and leaving little room for ambiguity. The problem is, people don't want language to work that way. It's not specifically that they want it to be hard to learn, but they want a language with nuance and ambiguity. We like puns and plays on words. People often enjoy and appreciate slang, or unusual word choice.
I am an American English speaker who has taken the first step to learning Japanese. One of the first things that confuses westerners about Japanese is the four alphabets, two phonetic (hiragana and katakana), one symbols borrowed from Chinese (kanji), as well as the English alphabet. Why not standardize the whole thing on English, and get rid of the rest? Well, then I discovered Kanji puns. There are different pronunciations and meanings for each Kanji, and they can be used in various ways to create double and triple meanings. The Japanese love to use Kanji puns. So, yeah, no one is looking for the optimally simple language. People want a language that the average people can communicate in, and the clever people can be funny and interesting in.