They're not worth more. The number of shares is increased by the amount that was issued. So that larger amount of equity is split among more shares.

A simple example:

Current equity of $100B, 100 shares outstanding. Each share is worth $1B, with 1% of voting power.

Then we issue $10B of equity via 10 shares.

Now we have equity of $110B, with 110 shares outstanding. Each share is still worth $1B, except each share now has 1/110 of voting power, instead of 1/100. Each share now only controls 0.91% of the company. Their ownership has been diluted.

edit: You can throw this comment thread URL into your favorite clanker (Claude, Gemini, whatever) and it will confirm exactly what I'm saying.