I've been on the receiving end of attacks that were reported to be the size of more than 10tbps I couldn't imagine how I would deal with that if I didn't have a 3rd party providing such protection - it would require millions $$ a year just in transit contracts.
There is an increasing amount of software that attempts to reverse this, but as someone from https://thingino.com/ said: opensource is riddled with developers that died to starvation (nobody donates to opensource projects).