It's also a way to sterilize new issuance to employees, primarily senior management. In a very real sense, it can be a backdoor payment to management. Issue shares to management. Buy shares on the market. Net effect is cash to management.
If buybacks are funded by debt issuance, it's also a way to lever the company. Remember Apple and Carl Icahn? That particular episode looks a lot like greenmail. Apple bought back shares, mainly from Icahn, so that Icahn would go away. The buybacks weren't exclusively from Icahn, so it wasn't technically greenmail.
Only if you want to sell those shares in the very near future. A little while down the track when the stock price has dropped again, all that spent cash has just been frittered away needlessly, blown away in the wind.
Interesting way to put it
A secondary reason would be lack of better options to spend the money on (no R&D investment opportunities).
Compared to other sectors, tech is more efficient with its revenue, so it leaves more money behind, which is available to use for buybacks.