Japanese has 4 words for "If" each one is used in a different set of circumstances and has a slightly different meaning and flavor.
http://www.guidetojapanese.org/learn/grammar/conditionals#Ho...
While all of those circumstances are covered by the English "If", the flavor and connotation is lost.
Similarly with Japanese and personal pronouns.
There is one word for "I" in English, but many many words for "I" in Japanese, each with it's own flavor and implications.
http://nihonshock.com/2009/11/the-many-ways-to-say-i/
These other "I"s express additional information about the person using them. It's not that this information cannot be expressed alternatively, but it's very efficient to simply use the right "I" to convey the right meaning.