That's because making it easy to start your own company will only provide upwards mobility to <1% of the population.
My grandpa worked in agriculture, my dad in a factory, and I'm a software engineer. The only reason I became the first in my family to go to university is that in my country as long as I passed all my classes I was pretty much guaranteed to not pay a euro for attending university. I even went to one of the top 5 universities for CS in Spain, which might be crap compared to US ones, but economically I'm much better off than my parents.
Affordable university education can provide upwards mobility to a lot more people.
In most of the US, as long as you are sufficiently academically qualified, you can go to a public university for free or nearly so. The exact standards vary by state, but they are not all that rigorous. The federal government on top of this provides means-tested grants to anyone regardless of academic qualifications that for poor people is likely to amount to 50-75% of public university or 100% of a two-year college.
Where the US differs from a lot of European countries is a) a lot of people chase after their "dream" university, which may be private/more selective/out of state/etc and b) almost anyone can go to A university in the US, no matter how poor their grades. It just won't be free.
My grandpa worked in agriculture, my dad in a factory, and I'm a software engineer. The only reason I became the first in my family to go to university is that in my country as long as I passed all my classes I was pretty much guaranteed to not pay a euro for attending university. I even went to one of the top 5 universities for CS in Spain, which might be crap compared to US ones, but economically I'm much better off than my parents.
Affordable university education can provide upwards mobility to a lot more people.