Why? The transition from 1 BC to 1 AD doesn't.
Discussion
Because the number had not been invented yet and it's usefulness not yet quantified.
Ironic.
That's a fair point... I hadn't thought of that. Nevertheless, it's not unheard of to hear 2009, for example, also expressed as, "the 2009th year of our lord". Personally, I'd throw my support behind not changing this convention... maybe just because I like the idea of referring to 2009 as either "1 A₿" or "the 1st year of Satoshis".
Or AGB.
After Genesis Block.
Do we really care?
Were winning so hard if we end up debating this type of split hair. Don't we have bigger problems somewhere?
No. Bitcoin already fixed it.
PS... this convention is also consistent with not having a Century Zero - this being the 21st Century (or the 1st Century A₿)