I see a lot of decklists that list synchro monsters. But the decks themselves have no tuners in them. Zero, nada, none.
These decks also dont use ability that gives them tuners (like the 'Mark of the Dragon' ones)
What am I missing here?
Why do they put synchros in their deck if they dont have tuners?
There is zero reason not to run 5 cards in your Extra Deck, even if none of them are usable. It makes your opponent at least partially think you have more options than you actually do. It's even more important in things like Ancient Gear that sometimes use an Extra and sometimes don't. You should be making them think a UAGG is possible even if you're not running it.
Either those decks run by the use of Skills like "Mark of the Dragon - Head" to get the Tuners they need for their Synchros or they are bluffing.
There's also the highly unlikely possibility to e-con your opponents tuner to use for your own synchro summon.
Like the person said below people sometimes put stuff in the extra deck to bluff.
Especially in decks that lend themselves to synchros etc.
It may make the opponent more inclined tov hold off on using certain backrow cards just in case.
I don't see any picture of those decks you mentioned, so I can't know exactly why.
But I guess that they just put random Extra Cards in Extra Deck to distract opponents from their decks or their strategies.