Having children is generally a timebound thing. As can be a career, often within the same time period as raising children. It's not like people can retire and think "OK, time to have kids!" This conjunction inevitably creates tension and exhaustion.
Being an engaged parent is great fun, but it's intensive. Trying to be an engaged parent while juggling a heavy workload is especially difficult; people find solace at the office because almost anything is easier. In an era where work follows you everywhere - I work past midnight most nights when the kids are sleeping and for parts of most weekends - the tension is hard to escape.
I don't think most people don't want or resent their kids, just that it's another thing pulling you in more directions.
Do you have kids of your own?