The most of the points are quite obvious. So let's beginn:
It's not about sex! It is about hierarchy
When you are having a slave it is not about sex! It is about hierarchy.
Of course you use the slave for your sexual lust but it is not in the foreground. It is about hierarchy, domination. It is about train him to be a better slave for your needs, to see him serve you, to see him working for you. It is about trust, security, responsibility and perhaps affection/love! You want and take the responsibility for the slave. It makes you happy to have these responsibilities and you are proud of it.Because it is about hierarchy and not about sex you do not need to be horny to dominate a slave. If you want to become a drink, your feet licked or other staff you order the slave to do so. A natural Master sees the slaves always as a slave.