You have to drink more to get the same amount of alcohol.Not quite old enough myself, but indeed light beer in the 70s was considered a "beer for weak little men who can't stomach regular beer".
But it was cheaper to make, all Bud Light literally is, is Budweiser with more water. PERIOD.
So the brands wanted to sell it, bad.
So they came up with brilliant marketing - showing tough football players arguing they drink it because it "taste great - less filling". That is to say - the selling point was - you can drink more!
And it worked like a charm. The lemming American consumer ran out and bought it and bought it and bought some more
Miller = 4.6% ABV
Miller Lite = 4.2% ABV
Budweiser = 5% ABV
Bud Light = 4.2% ABV
Coors Banquet = 5% ABV
Coors Light = 4.2% ABV
See the pattern there?
It's like when food companies sell "diet" food. They really just sell you less nutrition for more money.