Most of the older devs I know aren't in the industry primarily for the money. Their wealth level may not be a large factor in their decision about whether or not to leave early. The ones I know who are leaving (including myself) are doing so because the industry has changed in ways they are not comfortable with.

I think there's some level of interest in that tech jobs are fairly cushy (can work from home several days a week, benefits are good) and most older SWEs usually have more of a passion for the field. There's also maybe more of a culture nowadays of continuing to work at least part-time through typical retirement age to keep your mind active.