why is belt drive better than direct drive?

The direct drive turntables do not have a belt wearing and pick up faster.
Sonically there are disadvantages only.

Sean has said it all. I have nothing to add to that, except that getting new belts can sometimes be quite a bit of a drag. Incidentally, beltdriven CD players, if TAS is right, seem to have the same sonic advantages over direct coupled ones, as turntables for vinyl.

As Sean said above, any variation of a DD motor is tranmitted to the platter. That's the big rub: speed changes. Most DD motors are constantly increasing and slowing their speed to adhere to the desired speed setting. These speed changes may be minor as a percantage increase or decrease of overall speed, however, even a miniscule change will affect pitch.

And perfect pitch is what it's all about, eh?

You are assuming belt drive is better when you posted your question. Not a good start...

I sell industrial inkjet coding equipment. Are 'drop on demand' inkjet printers better than 'continuous' inkjet printers? It all depends. It has to be dealt with on a case by case basis. So with direct drive and belt drive TT systems.

You need to ask yourself what do you the turntable to do. Yes, play music, of course, but there's more to it than that. All my TTs have been direct drive. I find it very hard to part with their strengths and am willing to work with their weaknesess (like isolation). Direct drives are for people who PLAY records.

Do you want to PLAY records?

The direct drive principle should have been the best, just as CD should have smoked LP. There has never been a Direct Drive TT, that I have heard, in the last 30 or so yrs, except the Goldmund Studio that has ever touched, even mediocre belt drive, or very old Idler drive systems sonically. The entire issue of Idler driven Garrard 301 and 401 as well as old Dual 1000 series tables , do present a substantial challenge to the best of today's belt drive systems. There is a life within those older models that eludes modern designs. Y. Sugano of Koetsu used the old Garrard 301/401 systems as a reference for his MC carts. I thought him insane untill I assembled one for myself and nearly passed out at the results. For people"who want to play records", there are plenty of great units available in todays market, belt driven to perfection. You can start with Well Tempered and you really wont have to go much further.........Frank