Maybe because Anglos sometimes pronounce e like i and ei is more common in english spelling for a long vocal?

To be fair, German "ie" and "ei" is one of the few special rules which make no sense (or lost their sense in time). The 'e' in 'ie' is Dehnungs-e for elongation, just a notation that the i is longer pronounced (like Wiese, Biene). (Special rule: if ie is at the end of a word like familie (latin familia) often it is a diphtong and both vocals are pronounced).

"ei" is a bit stupid, because it is not pronounced "ei" but like "ai" or "ay" (eg Mayer).