files missing ?> closing tag

ran into some “header information already sent” error messages and came across this article:

http://codex.wordpress.org/FAQ_Troubleshooting#How_do_I_solve_the_Headers_already_sent_warning_problem.3F

i downloaded a fresh copy of 3.8 onto my local machine and unzipped the file. there are a TON of files missing the closing php tag ?>

is this an error with the installation? should i bother to go in and insert the missing tags or is this normal coding standards for wp files?