Question: > 
> *In mathematics and computer science, a tuple is an ordered list of elements. In set theory, an (ordered) n-tuple is a sequence (or ordered list) of n elements, where n is a positive integer.*
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So, for example, in Python the 2nd item of a tuple would be accessed via `t[1]`.

In Scala, access is only possible via strange names `t._2`.

So the question is, why can't I access data in tuples as Sequence or List if it is by definition? Is there some sort of idea or just yet not inspected?

Answer: 
One big difference between `List`, `Seq` or any collection and tuple is that in tuple each element has it's own type where in List all elements have the same type.

And as consequence, in Scala you will find classes like `Tuple2[T1, T2]` or `Tuple3[T1, T2, T3]`, so for each element you also have type parameter. Collections accept only 1 type parameter: `List[T]`. Syntax like `("Test", 123, new Date)` is just syntactic sugar for `Tuple3[String, Int, Date]`. And `_1`, `_2`, etc. are just fields on tuple that return correspondent element.
Apart from the benefits Jean-Philippe Pellet already mentioned this notation is also very common in mathematics (see <http://en.wikipedia.org/wiki/Tuple>). A lot of lecturers append indexes to tuple variables if they want to referring to the elements of a tuple. And the common (LaTeX) notation for writing "with index *n*" (referring to the *n*-th element of the tuple) is `_n`. So I find it actually very intuitive.