those people fixing the roads are incentivized to do the work cheaply so they can skim more “off the top”
And you still need to fight corruption to some level or it will come to a point where there’s more skimming than work being done
this incentive exists with or without corruption
without corruption you could do a shitty job once and then you won’t get another contract because you did a shit job
with corruption the quality of the work won’t matter so in the extreme case you can deliver nothing at all and you’ll still keep getting contracts - In my country we call this being “plugged in”