Why is Glycol transfer fluid still being used when low maintenance drain back systems could be installed ?

Why is Glycol transfer fluid still being used when low maintenance drain back systems could be installed ?

I now know that glycol solution needs to be replaced if has been overheated else it fails to protect systems against freezing and causes destructive corrosion. Glycol systems need to be regular cleaned / flushed out - if you can find that rare commodity - a  competent regular service provider.



I do not wish to return to the hassle and complexity of a system with glycol  in the heat transfer fluid.  I would prefer a simpler drain back system requiring less maintenance as described below thereby  reducing my dependence on a rarely existent product support services.


https://www.uksolarenergy.org.uk/drainback-system.html


https://www.solarhotwater-systems.com/understanding-solar-hot-water-systems-the-drain-back-design/


https://www.aetsolar.com/assets/files/catalogaugust2015optimized.pdf


https://www.installeronline.co.uk/vaillant-introduces-solar-drainback-to-commercial-market/



https://ecorenovator.org/Downloads/My-DIY-Solar-Hot-Water-Drainback-System.pdf