Question

1) Why do SETI fans think searching for extraterrestrial signal is worth the effort?

2) Why do SETI critics think the effort is wasted?

Answer 1

1) If We do CBA of the SETI mission then Benefit far outweigh any amount of cost as it can potentially resolve a lot of unanswered mysteries of the origins of life in Universe. We can have knowledge about different type of lifeforms and how they sustain, If the ET life is intelligent then there is potential of learning something from them, If they have better civilization than Ours with alternate fuels or harnessing the energy of their star system then We can accelerate human progress at an exponential rate. Their potential inventions can be beneficial for Earth's pressing issues like Global warming or Climate related diseases.

2) The effort is not wasted per se but rather the probablity of a success is very low. With taking the sheer size and scale of universe into account, SETI initiative is nothing less than a micron distance in front of millions of miles.

The limits of human technology also binds us as We are still not able to conquer even Our Solar system. If there was an intelligent life in Solar system, it is likely they would have made contact by now,

Also, the success depends on a number of factors as defined by Drake's Equation with multitudes of planets, there are very little number with life inducing potential and keeping in mind that life has evolved there, the success requires that life to be atleast on the level of intelligence present in humans. Also, even if they get signals, it is very rare that they also possess the technology to get it back to us fast enough.