Because market cap is just the crazy value investors have attributed to the company. It doesn't mean the company is any bigger or smaller.

But it means their cost of capital can be lower - for example, by issuing new shares to capture some of that high market cap. Then they can expand much easier than a competitor who cannot get such good rates for new share issuance.

They kind of can.

Example: the australian PM who repealed their carbon tax, is now working with his coal baron buddy on a green hydrogen plant. He's now calling for a ... brace for the irony ... carbon tax to help his new business.

edit: correcting myself, getting two PMs mixed up, Turnbull scrapped new Carbon Tax plans while PM, under pressure from Abbot (who he replaced as PM), who in turn had scrapped an existing carbon tax. Still demonstrates the slow shift of the well-connected politicians to follow the money.