20% of a crawler is fetching and parsing pages, the remaining 80% is dealing with misconfigured, broken and non-standard web servers and HTML. Dealing with Cloudflare, Akamai and random bot-busting tools that cause more false positives than a chaos monkey. It's better to write one yourself that you can control, monitor and operate as you need, instead of relying on third-party logic. Makes sense for my business, at least.
