It's because non-monetary benefits are a good way to attract talent in a tight labor market, which is more or less how the software developer market has been for the past twenty years. Developers like going to conferences, so they like working for employers who pay for them to go.

Think about why tech companies provide ping-pong tables and nap-chambers (obviously unproductive) and yet Wal-Mart isn't sending its warehouse workers to warehousing industry conferences (presumably at least somewhat productive).