Because the world of today is mostly better than the world of the past. OK, sure, you can find (or manufacture) counter-points to that by being extremely selective in what you consider "the past", but on balance, technological and social/cultural advancement have made the world a better place. So there are some peaks and valleys in a graph of some hypothetical "world happiness / goodness" index, but so what? If the long-term trend is "better", I'm not too bothered by the idea that "right now" is a local minima.

What do you look forward to in the world of the future?

* The continued advancement of mRNA technology, to enable rapid development of vaccines for new diseases, and new treatments for existing conditions

* Fusion power to provide nearly limitless, clean, cheap energy

* Improvements in desalinization technology to make clean fresh-water more readily available

* Nearly ubiquitous electric vehicles that use the clean energy from fusion (and solar) to provide transport without spewing carbon into the atmosphere

* Even better AI to develop new drugs, and newer, lighter, stronger building materials, and better battery chemistries, etc.

* More advances in genetic engineering to enable the creation of better crops that can, e.t. withstand drought conditions better, to stabilize food supplies, etc.

And so on. Generally, I'm bullish on what technology can do for us. What I'm less bullish on is human nature and our ability to use newer technologies wisely. But even there, I think that we, as a race, will eventually "grow up" and find ways to avoid some of our own self-destructive tendencies. Maybe that part is wishful thinking, but it's where I'm at right now.