The point with a syn flood is to try to saturate the OS limit for open sockets. From an attackers perspective the whole point of a syn flood is to do a DOS without needing much bandwidth.
My experience form 15 years working in the hosting industry is that volumetric attacks are extremely rare but customers that turn to Cloudflare as a solution are more often than not DDOS-ing them self because of bad configured systems, but their junior developers lack any networking troubleshooting skills.
