I have a store with Magento 2 on a server with Ubuntu 16.04 + PHP 7.0 and I do not know why when I activate the developer mode running:
php bin/magento deploy:mode:set developer
I do not load styles or JS and when I change mode executing the command:
php bin/magento setup:static-content:deploy
Yes it works but I need to load them in developer mode so I do not have to change mode every time I make a change.