Tubeless system is more expensive. Tubeless tyres cost more, you may need new rims, and you will need more paraphernalia such as special pumps, special tools, and special flat repair kit, thus maintenance cost is higher and more time-consuming to work on. Some tire manufacturers will recommend using their tires only with certain rims, and vice versa; wheels and tires are strictly matched to each other which limits you as to which tire you can use. Removal often requires good grip strength and strong tyre irons. If a tear or hole is too big for a tyre plug, you’ll still need a spare tube to get home. Air and sealant can escape (burping) if the tyre bead comes away from the rim due to a sudden impact or extreme cornering force. Sealants that coagulate need topping up every six months, and the more you put in the sealant the more the tire weighs and will upon the 2nd top off will weigh more than a tube tire will. Valve cores clog up too.
And the flat sealant doesn't plug all holes, only tiny ones below 6mm, and some sealants need to have holes less than 4mm; this means you will still need to carry a spare tube.
Some tubeless tyres, however, can take much more time to get fitted to the rims and involve much cursing. The problem is due to there being no one standard that all rim and tyre manufacturers adhere to. Also, because you need a very good seal with the tyre bead on the rim, it generally involves a very tight fit... in some cases so tight that you need multiple tyre levers, some soapy water to help slide the bead on...try that with a flat on the road!
A Continental GP 5000 TL 28mm tyre weighs 340g versus 250g for a regular GP 5000 tyre. Removing the inner tube, however, does save you in the region of 100g (but there are a lot of tubes that weigh less than 80 grams) but you're adding back 50-60g of sealant which negates some of the weight saved, and those tubeless valves are probably a little heavier too, and there's the rim strip if your wheels need it. Then in 3 months you have to add another 50-60 grams of sealant, now your tyre weighs more than the tube tyre would have.
So no, it's not all roses with tubeless tyres.