TL;DR: We vote on everything. 90% of everything is crap.
On Programmers, we are rather sensitive to poor migrations. Every day we get dozens of people suggesting reposting off topic, too broad, unclear, and opinion questions on Programmers.SE (see Duga's Playground and the historic Please stop using Programmers.SE as your toilet bowl). I will not tell someone to repost a question that will get closed on another site to post on the other site.
Anecdotally, most people just repost the question even if you tell them that it needs to be fixed before it could be appropriate on another site. If one says "this should be posted on Stack Overflow, after remove the call for library refrences and add an mcve" two minutes later it gets reposted without removing the request for library references or providing a mcve.
Many times, you will also see no attempt to migrate when the post is posted to multiple sites. Migrating at that point creates more work for Stack Overflow mods who would then need to close-duplicate the question and then merge it.
When we do want to migrate the question, mentioning Stack Overflow (as mentioned) will often mean the person will repost the question on Stack Overflow... and then the votes to migrate go through. More work for everyone around.
If you find something that you believe should be on Stack Overflow, flag it for migration. If you believe it needs to get moved sooner than later, jump into chat and ask for some help / attention on the question. There's often a moderator (who can do fancy diamond things if the question is already closed) and often three or four other users who can cast votes to migrate.
We get a fair amount of people who hit one quality filter on Stack Overflow or another and then repost here. Questions that have 'question', 'help', and the like in the title can't be posted on Stack Overflow. They appear to not be restricted here. So many times someone will try posting a (low quality) question on Stack Overflow, fail, and then try here and succeed.
There is also an aspect of how many votes people have to cast what. There are many days where I have run out of close votes. At this point, the only way to express my "this needs to be closed" (without custom flagging everything begging the mods to do it) is to down vote it.
Furthermore, you are seeing September in force. This leads to a fair amount of completely off topic questions being asked on Programmers.SE - people who need to learn how to debug. The answer to such is:
Step through with a debugger. Put printf statements everywhere. Learn how to debug. Putting the printf statement you have every other line would give you a better idea of what is going on. – MichaelT 9 hours ago
Suggesting these to go to Stack Overflow or migrating them would do a disservice to the person asking the question and Stack Overflow. The Stack Exchange layout is not well designed for pedagogy.
There is a lower rate of question asking on Programmers.SE. We get as many questions per day as Stack Overflow gets on some of its medium volume tags. This means that everyone can vote each day on (nearly) every post. And we do. Good posts get up votes. Poor ones get down votes. Its often easier to agree on the poor ones that are deserving of down votes.
Look at Users by votes on P.SE and compare it to Users by votes on SO. Our top voter has cast more votes here than the top voter on Stack Overflow, despite the site being a small fraction of the size. We have one of the higher votes per views (from Why are votes per post on the decrease (what can we do to improve this)?)
The way to say "no, Programmers.SE should not exist" is simple.
Have Stack Overflow accept that the questions that they want to send here should remain (and remain open) on Stack Overflow instead.
Provide the quality of answers that we provide here to the questions asked on Stack Overflow - both new and old. This involves active curation of the answers.
Make it easy to find the questions that don't require code and an mcve in some way other than using a meta tag.
Until these things are done, Programmers.SE has a distinct place within the scope of Stack Exchange.
I would also encourage you to read How can I encourage Stack Overflow to rein in the 'subjective' vigilantes? which has a bit of history for both Stack Overflow and Programmers.SE. That people are still misunderstanding the site and believing it to be "the site for everything that lacks code" or "NotProgrammingRelated" of old on Stack Overflow.