Instead of talking in the abstract about 'the benefits of meditation' in some sort of bid to convince others that they should be more like me, I can just speak to what I've directly experienced as reasons I consider my time investment so far (~2k hours over 5 years) to have been astoundingly worthwhile. YMWV
Having tranquility on tap has reduced flinchiness about not getting what I want. This has led to me getting more of what I want.
Being more able to emotionally let go of things that I deem negative expected value overall.
Strengthening the insight machinery for supramundane insight has carry over effects to mundane everyday insights. Investigation as a trainable skill.
Investigation and understanding of my own motivations creates much more affordance to investigate and understand others' motivation, which leads to fewer misunderstandings.
Investigation and understanding of the meaning-making process is similar, with the additional benefit of not being jerked around by others' meaning-making because I'm not desperately searching for a scarce resource any more.
Identifying commonalities between different goals simplifies much of life. Feel pulled in fewer directions.
Lessening of phobia due to ability to hold the fear reaction as object, running your own exposure therapy.
Keeping your identity small is much easier when you can directly detect the moments your identity tries to attach to things.
The skills surrounding Mindfulness Based Pain Reduction apply to both physical and emotional pain, and lead to dramatically less worry about sickness, aging, and death.
Increase in empathy making it much easier to get along with a broader variety of people.
Less reactivity makes life feel like it is happening at a more relaxed pace. Measurable as decreased neuroticism, the biggest quantitative effect size that I know of. I went from 60th percentile to 5th. This probably has immune system benefits.
For most people phenomenological time increases in speed with age. This is a loss since life satisfaction goes up with age (assuming good health). Meditation appears to not only antidote this but have a large effect in the opposite direction. A year easily feels much longer to me than it did a few years ago.
Less time and energy wasted trying to change others for my own benefit and less efforts needed to obfuscate that with various theories about it being for their own good.
Less attachment to belongings means my living conditions can only get so messy, I just don't have that many things. This is a bigger load off than you might imagine as Marie Kondo has been trying to politely inform you.
Easier to stay honest and avoid gossip (harder in the moment than obvious) = less to keep track of.
Abandonment of transactional frames in the social sphere. Confidence in ability to create value for others via many of the items on this list.
Dampening of comparison mind leading to much greater ability to appreciate moment-to-moment experience for what it is. (I couldn't have written an extended gratitude post like this before.)
Less oblivious to the social bids/connections others want me to match. Less need for approval.
Reclaiming of lost basic experiences of life in the sense of the SSC post What universal experiences are you missing out on? due to path-dependent childhood maturation.
Sense of a virtuous cycle of gaining more slack and reinvesting this in gaining more slack.
Finding that thing that you were convinced existed when you were an angsty teenager, convinced the adults were all missing something.
(Some context: a significant chunk of this came out of discussion around the legibility of progress metrics and the experience of opening up entirely new dimensions rather than just improving existing metrics. See also Robin Hanson on discovery of new considerations generally being more important than fine-tuning existing considerations in a broad variety of domains.)