There is also an issue of transition, where there plausibly is quite an efficiency lag (months, at least) before people become get really set up, even assuming they are able to be as (or more) efficient.
However, I'd point out that many software companies have far more sales people than engineers. There has been this expectation that salespeople should fly out, and have meetings, meals, and expensive drinks with the companies they sell to. Now magically that's all vanished, but sales are still happening. The cost of some sales efforts has presumably plummeted.
Once the lockdown is over, I wouldn't bet on the company that keeps doing remote sales versus the company doing normal face to face sales.
And sure, they'll revert back, losing the efficiency gains once the government stops accidentally intervening in sales practices.
Personally, I struggle to focus at home, and I have a pretty ideal WFH situation. I am fortunate enough/foolish enough to pay for a trivial commute, but I'm simply more productive in-office. And I don't think it is just me, many many problems can be solved in-office quickly without having to set up online calls (or letting an email thread drag on for weeks).
And the larger attitude among my office was that working from home is a burden. We're all software devs, we all have no strict barriers to WFH, but most people prefer going into the office most of the time.