WP by itself does not disable those functions. This is a security mechanism of one of your plugins or theme that is disabling them. It is common practice for malicious code to be hidden by encoding it, and then decoding and executing it when the site loads.
You can disable plugins one by one until the function works to determine which one is disabling it. Logically any security related plugins would likely be the one’s doing it, and with good reason, i.e. Wordfence, Sucuri, etc.