Why do we not say: "I've gardened all day", which would be correct if we have finished gardening but we say: "I've been gardening all day"? We seem to do the same with other action words: cook, sew, clean, wash, etc.
We naturally tend to use Present Perfect Continuous in OP's context partly because it emphasizes the very fact being asserted (that the action has been performed continuously).
But more importantly, OP needs to note that there's nothing at all wrong with, for example, I worked all day. The main reason we're more likely to say I've been working all day is because the Present Perfect form implies a strong connection to the present moment (i.e. - time of speaking). Bear in mind that I've been doing it all day doesn't necessarily imply anything about whether you're still doing it - it just implies that if you're not still doing it, you only stopped very recently.
Thus you wouldn't normally say I've been working all morning in the evening, (unless there's some obvious contextual reason why working continuously several hours ago significantly affects and/or explains your current condition/circumstances).