Back in the 70's when the numbers for bowling were at it's peak the sponsors were focusing their advertising dollars on products that appealed to blue collar necessities, not the amount of disposable income which may be true for golf.
Examples such as shaving cream, pain relievers/aspirin, spark plugs (Spitfire), car tires/tuneups (Firestone/Goodyear), mufflers (Midas) the latest greatest car deals to be had for blue collar level transporation (they weren't pitching Cadillacs or Lincolns).
The advertisers always knew that a high level of disposable income did not exist in bowling market and therefore, big ticket items which produced large profits for the sponsors fell to the golf market. Hence the difference in the level of sponsorship/ prize funds.
There were differences then, now, and will be in the future because although they appear to be similar, in reality they are completely different markets in the world of sports.