I changed my prefix of my tables from the wp_ to something else for security reasons and good practice etc. I was curious most of new plugins installed take on the new prefix but I have one that refuses and still installs with wp_ it still works but i was curious is that normal practice or just a bad written plugin?
Short answer: Just a badly written plugin.
Longer answer: When a plugin calls the database in the right/correct/best practice way it uses Global
$wpdb instead of just naming the database table, for example:
$sql = "SELECT * FROM wp_posts WHERE... "
$sql = "SELECT * FROM $wpdb->posts WHERE... "
this way it would work even if you change your tables prefix.