Yeah I've noticed this. Saw a lot of it while walking around downtown Dallas, or Cityplace etc. Unfortunately US cities are uniformly terrible at maintenance, largely because labor costs are high and politics forces cities to keep taxes low. So rather than maintain streetscapes, civic improvements, etc we just let them deteriorate until everyone is sick of them, then get a big one-time capital investment to replace it all with the next flashy thing.
There are a few options to deal with this issue - since the public sector can't do it, there are various ways to privatize. One option is to create a Business Improvement District where commercial property owners voluntarily tax themselves to fund regular cleaning/trash pickup/maintenance, sometimes private security if the city will allow it.
For important parks/plazas, you can also create a conservancy which basically takes one-time charitable contributions and puts them into an endowment, then funds cleaning/trash pickup/maintenance off the interest on the endowment. I think several public spaces in Dallas were
done this way, Klyde Warren Park, Thanksgiving Square, etc by various semi-private (or religious) groups.
Or you can use a private development model like Domain in Austin or Legacy in Dallas, basically giving full control of the streets and public spaces to one large property owner or HOA who is responsible for maintenance. This can be a shopping/entertainment destination like Domain or just a mixed-use neighborhood. It's harder to do in an existing street grid area, but sometimes you do get large parcels with a master development in/near the inner city.
Nowadays I think there is an increased recognition when building a new park, plaza or streetscape that the long-term needs need to be considered and addressed at the beginning; the 90s were really the tail end of that reckless "free money from the Feds, spend it as fast as we get it" strategy. Now we are firmly in the neoliberal era of corporate involvement, sponsorships and privatization.