Last but not the least, many people are very ill-informed about GPL and how it works. I experience this when we discuss this with peers.
This is why I only use copyleft (or non-commercial/share-alike) licenses on what I build/produce/put out.
They mostly do not.
They only demand that you offer the source code to anyone that asks for it if you also distribute any kind of executable (you may even charge to cover the costs of the distribution).
The AGPL expands this to SaaS's too to close that loophole.