Past negative informal sentence before から


A native Japanese speaker said to me "見たことが ないから ～です。" to mean "because I
didn't watch it, …." (we were talking about a movie).

As I have learned the sentence structure using から is " _[reason: informal
sentence]_ から _[result: sentence]_ ", I felt this sentence was too
complicated. So I asked her if it was possible to say "見なかったから ～です。", as 見なかった
is the informal version of "did not see". However, she refused and said that
would sound strange.

So my questions are: why is the informal past negative form unnatural here?
Are there other informal sentences that cannot be used in front of から? What is
the pattern? Do the same rules also apply to other compound sentences (like と
おもう) and other situations?




見たことがない and 見なかった are different in meaning. So the grammatical structure of
〜から has nothing to do with the problem.

The meaning of 見たことがない is "have not seen" or "have no experience of seeing".

On the other hand, 見なかった is simply "did not see (at a certain opportunity in
the past)".




見たことがない and 見なかった are different in meaning. So the grammatical structure of
〜から has nothing to do with the problem.

The meaning of 見たことがない is "have not seen" or "have no experience of seeing".

On the other hand, 見なかった is simply "did not see (at a certain opportunity in
the past)".

