I wonder, why
! symbol is called exclamation mark, but
= symbol is called equal sign? Is it only tradition or there is something behind?
I suppose it's in the origins.
? and ! are from the family of language punctuation marks
= is from the family of mathematical symbols or signs.
I think they're called marks because they actually mark something. That a sentence is a question, an exclamation, or a quote.
= is just a sign, it doesn't mark anything.
Again, this is just another guess.
Another difference I see is that the exclamation mark has no meaning on its own. It is merely punctuation whereas the equals sign actually adds meaning to the sentence: life "equals" goodness.
I cannot comment yet, as my karma will not allow it. The exclamation mark was referred to as “sign of admiration or exclamation” in the 15th century according to http://en.wikipedia.org/wiki/Exclamation_mark
I think it is just convention.
If you think about the = sign, you can argue it "marks" equality. On the other hand, if you use "exclamation sign", in my mind, the street sign pops up.