I guess that's the nature of the beast. Who's motivated to write a review saying "Yep, great service. Won a few £££."
Coral don't do too well: https://www.trustpilot.com/review/www.coral.co.uk
Ladbrokes are atrocious: https://www.trustpilot.com/review/www.ladbrokes.com
Paddy Power are toilet: https://www.trustpilot.com/review/www.paddypower.com
Bet 365 are shocking: https://www.trustpilot.com/review/www.bet365.com
etc.