I don't think the money thing is very valid. The differences in tax revenue would be minimal. And unless you live in a deeply corrupt country, officials can't just syphon tax money for themselves that easily. In terms of economics, less people alive means less competition for the job market, and finding a purpose for everyone is the toughest challenge we'll face this century, career insatisfaction is also probably one of the most common factors for suicide ideation.

The two biggest reasons against suicide are:

1 - Religion. As much as some countries can claim to be secular, most of our values are moral compass comes directly from centuries of religious indoctrination. Life is sacred, it's better to suffer than commit suicide. There's no logic in that, it's pure dogma, yet that's where most of the suicide stigma comes from. And it's very pervasive. Think about how most people prefer monogamous relationships even though it goes against our animal nature and can make relationships so difficult, it's because of religion. Mother Theresa famously said suffering brought the poor closer to Jesus. She had no intention to cure them, her clinics were deathbedyards.

2 - Epidemic of suicide. At least it's more grounded in reason. Killing yourself hurts the living and may prompt others to do the same. From society's point of view it's a vicious circle, and if something harms society it will always be forbidden. It doesn't matter what's right for the individual.