... why do so many scofflaws keep using “I” instead of “me”? Perhaps it’s because they were scolded as children for saying things like “Me want candy” instead of “I want candy,” so they began to think “I” was somehow more socially acceptable. Or maybe it’s because they were admonished against “it’s me.” Anybody who’s had “it is I” drummed into his head is likely to avoid “me” on principle, even when it’s right. The term for this linguistic phenomenon is “hypercorrection.” A related crime that Mr. Obama stands accused of is using “myself” to dodge the “I”-versus-“me” issue, as when he spoke last November of “a substantive conversation between myself and the president.”
Or, a fondness for the first person singular and the intensive myself may simply reflect egoism. I would add that just because there are precedents for these usages doesn't necessarily justify them. Incorrect speaking and writing take place all the time. There still remains correct speaking and writing. Shakespeare created characters - their mode of speech may reflect their standards, not his.