Pinyin IMEs are still much more popular than Wubi IMEs because of the latter's steep learning curve. Pinyin was designed by Chinese for Chinese learners, and is only incidentally used by westerners. It is based on the latin alphabet yes, but its how all the school kids in China learn standard pronunciation of mandarin words (indeed, this is pinyin's main purpose). So pinyin isn't really a foreign concept to any Chinese who has went to school since the 60s.