Has Rockstar explicitly said why they aren't developing for PC?

I can imagine they made a fortune off PC going by the amount of times GTAV has appeared in the top selling lists on steam.

The cynic in me says it's so that they can use the same strategy that worked so well for them last time. Release on these consoles first and get everyone excited enough to go out and buy it. When the new consoles come out in a few years, do an updated version that also comes to PC. That way, they can likely sell multiple copies to people who want them on the new platforms as well.

This, no doubt, plus the added development time to release a stable and optimised version.

Like said, it’s possible that a pc-version comes out at some point. But even if it won’t, they’ll still be swimming in money with sales from the normal game and later on from RDR Online (assuming that it’ll take-off as well as GTA Online did) and might not be too bothered from the lack of pc-version sales.

I have two theories.
The development of a Rockstar open world game is so large and involved that the studio focuses on the primary platform, which will always be the console.
or
GTA5 was so brilliant that fans bought the game multiple times, it came at an opportune time for Rockstar, the end of the last generation, the updated version for modern consoles was very much desired, then also the PC version, i'm sure Rockstar through the social club can see how many of their players bought the game multiple times, and that staggering the release of the game benefited them in the long run.

They must have really good data on who owns it on both PC and console thanks to Rockstar social club. That's my guess. I've done it for GTA 4 and 5.

Why launch on PC when you can release it on PC 12-18 months later and get those double dippers? GTAV was huge on PC, so there’s no doubt they’ll do it eventually.

Tradition.

I think it might be a little bit different this time around since new consoles aren't as certain as they were back in 2013 when GTA 5 first came out. The PS4 was released only a couple months after GTA, so players didn't have to wait long if they bought a PS4 and wanted to play it on there (it did come out over a year later but players knew what they were getting once it was revealed at E3). Now we have RDR 2 coming out at the end of next month, nobody knows anything about any new consoles except for hearsay and vague information, and PC obviously isnt changing or going anywhere. This has me thinking that they're going to put all the work into the PC version after this one is released since it would be ridiculous to make PC players wait a few years for PS5 and Xbox Googolplex to come out before they start working on a version they can play.

I think some of it is that without a pc release at launch they dont have to worry about piracy. Anyone who wants the game needs to buy a console and the game. Plus they have more control over stuff like the online and I assume can monitor that side for best dlc money making.

I highly doubt double dipping is the reason for the PC delay, given how popular MTX are in GTA Online releasing RDR2 sooner would yeld far more over a few folks double dipping.

The answer is probably akin to Valve time.