I guess at the end of the day its a signalling effect on what they use cash for. Ideally, most tech companies would like to keep 1-2yrs of operating expenses as cash to avoid any massive techonological recessions or to combat failed products. However any dividend or buyback would signal that apple no longer have any project where they can invest surplus cash and generate risk adjusted returns which are more than WACC for shareholders. That would be a bad signal for any growing tech company.

However, Apple could try to diversity its product line and can massively fail/succeed if required or think of using the cash at a better place like M&A (pitfalls or accretive etc) or just decide to keep it on B/sheet and decrease purchasing power.