They are designed to release kundalini. It is not clear that releasing kundalini has anything to do with ultimate happiness.
Thinking that getting more spiritual leads to happiness is a common assumption, but it is not necessarily true. First of all, if your body is not pure, it just leads to sickness and even death. It is essentially the same as overdosing on drugs. The more pure and transparent to energy your body is, the more difficult it is to overdose.
But let's suppose that you are pure enough to process kundalini constructively rather than destructively. Think about even the most immediate powers that it grants to humans, that of reading minds. It takes a superlative human to deal with all the negative thoughts that people send your way.
But let's suppose that you are so pure that the negative thoughts do not register. Then you face the temptation to abuse that power of insight for your own selfish purposes. Thepower of prophecy is another benefit, or albatross that is easily abused for your own selfish purposes. And that is the worst kind of karma- to abuse an inherently spiritual power. Almost all people are much better off avoiding kundalini and relying on intuition for the same benefits.
Good inituition, if you knowhow to read it, can guide you through life without the negative benefits, for as soon as you abuse it, it goes away. And regarding reading minds, reading body langauge works just as well.
But again let's suppose you are sufficiently powerful and pure and spiritual and perfect that you can avoid the all the spiritual traps that lay in wait of your arrival. By the way the early books of Castenada spell out these traps rather explicitly. The first is fear. Kundalini is scary. The second is power, what I have been talking about above. The third is understanding. You stop progressing when you think you understand everything- it's something like ego, the last barrier to being enlightened.
The point is, if you can overcome all these traps, what you end up with is the burden of being responsible for the whole world, and feeling the misery and agony that exists in the whole world. That is not a very happy state.
I for one am content to be at the bottom of the spiritual ladder where I can accomplish my purpose in life with relative ease, and come back again and again, gradually taking on more responsible roles.