I assume this cleaning includes putting them in your trash and the city taking them to a landfill?
It's obviously not the best path, but cities[0] (by necessity) generally do a good job cleaning up the trash that gets scattered around.
Bigger issue is non-urbanized areas where there isn't the density/wealth to clean up litter.
[0] The collection of people and institutions, not just the government.
People litter. Cigarette butts, straws, plastic bottles, etc. all very regularly and easily wind up in the ocean with an assist of a slight breeze.
(I would distinguish public trashcans like this from e.g. commercial trashcans for the use of customers of private businesses. First, they should never fill over halfway. Second, the whole thing should be kept clean. Anything else is a failure of management.)
And of course, all the other parts of the road that don't happen to run up to a yard are not really groomed, so all that debris is flushed into the waterways.
How do you think they generate statistics for this kind of thing? They don't count everything, they take samples and infer from that.
It's far more likely that I live in a stray straw accumulation zone than straws are uniformly distributed over the entire city's gardens by some method.
[0] https://en.wikipedia.org/wiki/Faulty_generalization#Hasty_ge...
Considering that a lot of land in a city isnt your garden/house (shops, offices, parks), I would suggest that that would tend to balance out the risk of this being a SAZ.
I take your point that this is a data point of one. But if I found one straw in my garden, it is astoundingly unlikely that is the only wild straw in my city. I wouldn't start putting a figure on it from that, but it does suggest the lower bound is much higher than one.
Having never found a straw in my garden my intuition is that (not finding straws in every garden) is more likely than (finding straws in every garden) but obviously I have no valid basis to put a number of any kind on that.
Now while I think the original post is an example of Hasty Generalisation, I think the bigger issue is the generalisation combined with a sample bias. Self reported data points tend to be interesting because otherwise they wouldn't be reported. My thesis is that regularly finding a straw in your garden is interesting because it is unusual.
My front yard disagrees. It's adjacent to a somewhat busy road, and straws are part of the debris I have to routinely clean up (along with various wrappers and cigarette butts).