said by Kearnstd:because stock holders dont want to see their money spent on future proofing the network when the existing one makes them more money in the current.
And what is your reasoning for this statement? Look at any stock valuation method, Discounted Cash Flow, Free Cash Flow, Dividend Discount Model, all of them focus on pricing future growth and income. Key word being FUTURE. The capex(capital expenditures) on "future proofing", as you call it, would be well received by all shareholders, as it would allow for sustainable growth in cash flows received both in the form of dividends and capital gains.
The actual reason this is not done is due to the loss of management incentives as they would, more than likely, be unable to meet their goals, probably in the form of net income or cash flow goals.
This is known as the Principle-Agent problem.