@itaydvir As Magnus said, sane log files do have a newline character at the end of each line.
Specifically, though, because the file input is designed for tailing, the fact that an EOF is detected cannot be interpreted as end-of-all-input.
The LS file input as it is now, has no option to set that lets the user indicate that EOF means end of all input and even if there was it could not be the default, meaning that the user would have to read the docs to understand when to use it - and in reading the docs one would see "By default, each event is assumed to be one line." as the first written line (characters before a full stop character) of the second paragraph. I'll admit that it does not actually state that a line is defined as all the characters before a newline character. This is because the file input is used to read variable length lines not fixed length records and the end of variable length lines are terminated by a newline character, see this.