Because I can and have played them. Their combat is not turn-based. There are no turns. Since we started this conversation I have browsed the Internet both for the original claim made by Todd Howard and for any source that describes combat in Bethesda's games as turn-based or close to turn-based and have not surprisingly come up completely blank. If Todd Howard or you want to claim that combat that is prima facie not turn-based is in fact turn-based due to some mystical voodoo built deep into the Gamebryo code for reasons that remain unclear it is up to you to provide the evidence. So far you haven't even given me a source for Todd Howard's plainly inaccurate claim.
Before this conversation goes any further, you really http://en.wikipedia.org/wiki/Time-keeping_systems_in_games
(The "Ticks and Rounds" section is particularly relevant to this discussion.)
Turn-based gaming goes far, far beyond your definition, especially in the electronic gaming realm. I've been playing tabletop RPGs for almost 30 years now (and PC ones for almost as long), and I can reasonably testify as to what constitutes a "round" or a "turn" in gaming -- and you bring up "mystical voodoo" within the Gamebryo code, but neither can you conclusively use it as proof in this instance.
As for past developer comments, there was a particular issue of either
Game Informer or OXM dating back to around 2006-07, as well as in at least two separate video interviews I've seen with Todd and other members of the Bethesda dev-team where "turn-based [play]" was explicitly mentioned in context with
Oblivion...and no, before you ask, I don't have exact links, issue-numbers, etc., because it's incredibly late, I'm tired, I have to be back at my firm early in the morning, and because this is a subject that should've shrivelled up and died three pages ago.
Just for the hell of it here are http://www.ataniel.org/oblivionreview.htm http://www.gamingexcellence.com/xbox360/games/427/review.shtml for Oblivion in which combat is clearly described as real-time. There are many more. If you can find me a single review, or even a statement beyond Todd's still unsourced claim that combat in Oblivion is turn-based or practically turn-based I will be amazed.
It would be except I have access to the very game he was describing and it is most certainly not turn-based.
Hold up, though...you're not actually going by magazine reviews for your argumentative-support on this one, are you? Third-party, outside reviews aren't sufficient proof to substantiate your claim. I have "access" to that same game, too, and I'm pretty sure it got reviewed by that one frat-broseph at that one school for his campus newspaper, where he also referred to it as "real-time combat."
It doesn't mean he had formal experience in C++11 coding or RPG design.
The combat system keeping track of what is happening on a moment-by-moment basis does not make the game turn-based, since the actors involved may well be doing so simultaneously. In turn-based battles, only one side at a time may act and the results of any offensive actions are resolved upon the other side before it gets the chance to respond. As a result, it becomes vital to maximize the number of actions one is eligible to perform, how many of same one can perform within a turn's 'time frame', and the chance of getting to act first. This is vastly different from how a RT game works, since combat performance optimization in such games follows a completely different set of parameters.
Morrowind, Oblivion, FO3, and F:NV are most definitely not turn-based in any way, since all action (even VATS, although the opposition is slowed) is real-time and resolved simultaneously.
Again, take a look at the breakdown-link I posted above -- there are many different types of "turn-based gameplay," some of them not directly adhering to that specific definition (which is one of the more commonplace versions out there, to be sure).