Why subtitle content is hard to read
A subtitle's break doesn't look for the end of the sentence, but for the point where it stops fitting on screen. The usual convention is two lines of about forty characters, visible just long enough to read, which splits sentences without any regard for punctuation.
That's why opening an SRT in a text editor is hard to read: stray numbers, interleaved timestamps and sentences broken every two lines. This tool not only removes the numbers, but reassembles what was split to produce readable text.