Why? Because English is used as the "official internet" language and so a large portion of the English texts on the internet is written by people whose first language is not English and whose command of English is rather poor.
I see no difference in "until" and "till." Till is not a shortened form of "until" either - you may find this interesting: World Wide Words: Until, till and ’til
It includes this: The most common belief is that till is a shortened form of until. You can see how this could have grown up, but the truth of the matter is that till is by far the older word, being recorded from about the year 800, while it took another 400 years for until to appear in the language (it’s a compound of till with the archaic Old Norse und, as far as, which also survives in the archaic unto). But the first sense of till was to, as it still can be, for example, in Scots and some dialects. Though the modern sense of till in standard English is always connected with time, this only appeared about 1300.
as well as this: , ’til, has been created within the past century by people who believe that till is an abbreviation of until and want to mark it as such. It has often been said by style guides and dictionaries that it’s a mistake and it arouses passion in some people. Most recent writers on language prefer to describe it as an informal version of until
Anyway, I don't know if I'd say "From 8 to 8" or "from 8 until/till 8" but I wouldn't regard it as an error if I heard or read it.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
"until," O.E. til (Northumbrian), from O.N. til "to, until," from P.Gmc. *tilan (cf. Dan. til, O.Fris. til "to, till," Goth. tils "convenient," Ger. Ziel "limit, end, goal"). A common preposition in Scandinavian, probably originally the accusative case of a noun now lost except for Icelandic tili "scope," the noun used to express aim, direction, purpose (e.g. aldrtili "death," lit. "end of life"). Also cf. Ger. Ziel "end, limit, point aimed at, goal," and compare till (v.).