Is bypassing scraping blocks the main purpose of these residential proxy networks?

Yes. For instance, Bright Data describes itself, on its home page, as the "all in one platform for proxies and web scraping".

	▲	duskwuff a day ago \| parent [-]
		Oh, I'm sure there's all sorts of illicit use as well. But scraping is what the network is being actively marketed for, and it probably amounts to most of their traffic by volume.