Take Google. Their one, core cash cow is an oil strike. If you strip away all the unrelated and unesesarry.... It's an 80% profit business that represents most of www's monetisation.
Google already have all the market share. It takes >$10bn to meaningfully affect their bottom line and share price. Few of Google's many investments have an obvious chance of achieving this.
Still... The market (and Google's board) consistently prefer to retain (or avoid realising) earnings.
The fact that Google's growth requires almost no capital also generates an inward capital flow.
Google's culture was a good fit for this. First they let a thousand flowers bloom. Then the cultivated university-like subcultures. They alway knew how to spend big on blue skies.
FB is a little more awkward. They know where the bread is buttered. They invested more tightly around the core money maker, but they get to the same place as Google. Way more capital, credit and discretionary spending than they possibly need. Nothing more to invest in.
Well... All this is resources that aren't spent on manufacturing, tooling, energy, construction, etc.
Take chip fabrication, or computer hardware broadly... It's capital intensive. Factories change slow. Markets change fast. Prices continuously fall. It's a nightmare, comparatively.
I say "capital" but the real shortage is risk. Google/FB/etc are "hoarding" all the risk allowance. Where they can invest in highly speculative projects because the money is just there, analogue businesses are still backed by banks, bonds, specialised investment firms and tightly controlled payback schedules... Not an easy world to innovate in.
The modern system now reaches bedrock very quickly. When we can dig no longer we start depleting all our resources trying to dig anyway.
Reality is that were not getting more out of Google no matter how much resources they draw. That's what capital is to firm, resources. Over resources X and under resourced Y.