The stock will often have a pop upon such announcements but these are often not material in the grand scheme of things.
Sure a lot of things are not material in the grand scheme.
Here's the math, made simple by small numbers:
A company has $100 in cash, and 100 shares outstanding. The underlying enterprise is worth an additional $100. The company is now trading at $2/share as a consequence, each share being worth the $1 enterprise value plus $1 cash.
Plan A: The company pays a $1/share dividend. The enterprise value remains at $100 but the $100 in cash is gone, so the company is now worth $1 per share, and investors have $1 in cash in hand. Each investor still has $2 in value, but half of it has been converted to cash.
Plan B: The company spends $100 in cash to buy back 50 of the outstanding shares. The enterprise value of $100 remains, there is no longer cash on hand, and there are now 50 shares outstanding. Each share is worth 100/50 = $2 just as before. However, half the former investors now have $2 in cash instead of $2 in stock.
The distribution--who gets the money--is slightly different but mathematically it's the same. One way or the other the company has taken that $100 and distributed it to shareholders. All shareholders still have $2 in value aftewards, but after the transaction some of the $2 is stock and some of it is cash.
The stock buyback has one key advantage over the dividend: Under the buyback it is the investors who decide whether they will convert to cash, and how much of their holdings they will convert. Under the dividend some of their holdings are converted to cash regardless of what they wanted. Moreover under the buyback investors can choose which year to convert, maximizing their tax position. Under the dividend they have no choice--they receive the dividend when it is paid, paying the tax in that year, like it or not.
Any actual change in value resulting from either a dividend or a stock buyback has more to do with what the company is communicating than what it is doing financially. A company executing a stock buyback is communicating "we think you understimate our enterprise value", while one paying a dividend is saying, "we are making profit as usual". It's really a communication from management more than anything else. Sometimes it's a tax game.
No financial trick, such as a dividend, or stock buyback, will increase an investor's net worth--only move it around.
However companies can and do increase net worth of investors, as I previously described--by the physical creation of new goods and services, creating new value that never previously existed, and adding that to the value of their enterprise. We call this "profit".