Why are so many US bus systems/networks doing redesigns or refreshes now, including ones that have happened in the past 2-3 years and in the near future?

I've noticed that so many cities are having bus network redesigns. Dallas has one in January 2022, New York City had a smaller one in June 2022 (Just for the Bronx), Miami had one in November 2023. And Philadelphia, Atlanta, Detroit, New York City, Boston and Washington D.C., just to name a few, are some cities that have some redesigns planned to come out in the next couple of years.