Investing in capital goods, e.g. a new machine for a factory, sees a high but fixed cost and then a almost fixed return over the life of that machine that starts immediately as the business use the machine to produce more.
Investing in knowledge, e.g. training people, sees an ongoing cost with an uncertain and variable return in the future as people learn how to utilise their new knowledge in improving productivity.
Assuming that investing in knowledge will provide the same returns profile as investing in capital goods could lead organisations not invest sufficiently if they recognise that they didn’t get an immediate return in productivity from the investment but don’t understand why.