Aside from the political problem posed by mobilising the Kyiv/Dnipro/Lviv middle class who don't want to fight, those "able-bodied men in their 20s and 30s frequenting gyms, bars and hip restaurants" are the people who are just about holding what's left of the Ukrainian economy together. To be crude, they're the men who Ukraine can't afford to see killed en masse while their economic situation is as fraught as it is and millions of young Ukrainian men are still in Europe with no intention of returning. The EU and the US are squabbling about the money they already provide to Ukraine. Total mobilisation would require many more times the amount of economic aid they're already providing only to keep the economy afloat, let alone to train and arm another half a million soldiers. As Zelenskiy said in his press conference yesterday, it's the most politically difficult question he's faced. It's not as simple as "Ukraine needs total mobilisation and the West needs to pay whatever it costs". He's got several very complex interests to balance at once. Western leaders are trying to move away from the narrative that Ukraine is fighting for global freedom (it's hard to keep pushing that angle when at the same time you're making Zelenskiy come over to Washington to literally beg on camera for the financial and military ability to, as Biden used to put it, "defend America's own national security") and shift it back to Ukraine alone, i.e "Ukraine is fighting for its very existence" (John Kirby yesterday, the first press conference in a long time he hasn't gone with the sky-will-fall "Ukraine is defending Western democracy" narrative). Another thing that was clear from Zelenskiy's press conference yesterday is that both Zelenskiy and Putin are laser-focussed on their goals, but the West is not. The West has no clear aim for this war. They don't even know if they want Ukraine to win it. Before mobilising half a million more men who don't want to fight (or else they'd already have volunteered), and the enormous political pressure he will receive if he does that, Zelenskiy will need an absolutely iron-clad guarantee from the West that the economic and military aid will not stop, in fact will be massively ramped up, at least from now until November 2024. So far he's not getting that guarantee, in fact all the signals he's receiving point the other way.