In this area, Illinois, people who have been married a ceremonial number of years (5, 10, 20, 25, 50, even 75) like to commemorate the event with a Mass of Thanksgiving and a party or reception of some sort; the more years, the more formal the Mass and the bigger the party. It helps to have lots of kids who are now adults to help pay for it, but those are not always available.
Part of the Mass usually involves the priest, after the homily, making mention of the occasion if it is not a “private” Mass (because there are no such things as private Masses). He mentions how long the couple has been married, a few ancedotes of their lives, and how they are still together. If they choose, the couple renews their marriage vows, and/ or the priest has a special blessing for them.

If he’d rather not but she would, his bride of 25/50/75 years will usually know (by now!) how to get her old goat up there to do it.
I once saw a very sweet and poignant exception to this. The couple, married 50 years, participated as always at early morning daily Mass. However, it was the actual day of their anniversary. Without a lot of fanfare, they renewed their vows at daily Mass, received the Eucharist, and then took off for a honeymoon- at Wisconsin Dells, as they did 50 years ago.