I can honestly say I am glad I dontspendthis much time thinking about the Star Wars Universe lol.

Wow.

Well if we can accept that Jedi give up love, attachement, passion etc... because they believe in Jedi teachings well then it is just as plausible that Sith would understand the risks they take in bringing on an apprentice and do it anyway. Keep in mind the master controls who their apprentices are and, by and large what they learn. One of the things that I like to think made Palps such a formidable Sith is the constant state of fear he must of lived in of his own apprentice and his apprentices son Luke.

I think the simplest answer to the original question is this:

Sith Lords are lonely.

They spend their entire "career" on the quest to obtain more power. They use subterfuge and deception to achieve this goal and in their wake leave only death, destruction and suffering. But once you gain this power, who do you lord it over? Who is your personal sounding board for your enigmatic and evil plans? The so called "ying" to your evil "yang"?

It is obvious that previous incarnations of the Sith Order did not work when there were many Sith Lords and many disciples. They bickered, and fought, and destroyed themselves from the inside. "My lightsaber is bigger than yours" mentality drove the final spike into the proverbial coffin that constantly plagued the Sith Order. Bane saw this and knew the Sith needed to compartmentalize to the extreme. But he also realized one thing, even for a Sith: everyman is an island. The Darkside would drive any force user mad if he or she did not have a "companion" of sorts to compliment one's own eccentricities. Darth Bane would not have become a bold new Sith ushering in a legacy that will follow for centuries to come without an apprentice. Instead, he would have become a husk, a shell, vacuous and purposeless without an apprentice to look up to him, and constantly challenge and threaten his growth in the Darkside.

All the destruction and power is useless to a person who does not leave a legacy. He will be merely a page in the history book, eclipsed by those who live long after their dying breath, an everlasting impression left on the universe. A man is more than flesh and blood, but a churning ball of ideas and principals! A man is capable of influence and inspiration, fear and hate, love and kindness. None of this exists when you are alone. He who does not pass on what he learns will never be remembered!

And if you can't tell, I just BSed that whole thing. Reminds me of high school english class!