Because the country has been at war for 8 years and all help is welcome?
Many Ukrainians are quite pissed off that it took the US and UK this long to start sending serious lethal aid. Because those 2 (along with Russia) were signatories to the Budapest Memorandum. And yes, I know the Memorandum isn't legally binding, and Ukraine signed a terrible fucking deal that left it at the mercy of its neighbors. And yes, they should blame their own politicians (which they do. Very much so.) However, many Ukrainians very much buy into the West's moral posturing, and thus when realpolitik considerations happen, at the expense of Ukraine's interests, people still get angry over the hypocrisy. It's a growing pain, as a society and as a political nation Ukrainians are still fairly young and naive, and the overwhelming majority hasn't moved beyond the Cold War paradigms yet.
Thus. Zelensky is trying to keep things calm and keep the economy from collapsing. Loans and promises of loans are nice, but they don't replace money in the bank. And while Russia is obviously doing most of the harm (the Black Sea naval exercises, for instance, are blocking like 85% of the access routes to Ukrainian port cities, amounting to a deal facto trade blockade), the absolutely massive Western media hype campaign is exacerbating the economic downturns. Ukraine keeps repeating the same thing -- the amount of Russian troops is insufficient for a successful head-on assault on defended positions, where there needs to be a certain ratio of attacking : defending forces. Obviously, if Russia goes ahead and tries to level Ukraine with artillery, there isn't much that can be done; but there is very little Ukraine can do about that now. Civilian shelters in all major cities are being reviewed and restored up to code. Ukraine tried to buy the "Iron Dome" defense system, but that was blocked;
In the short-term, the government can't take any additional measures, beyond the current partial mobilization. Russia can maintain this readiness state a lot longer than Ukraine, so Zelensky can't afford a "waiting game of attrition".
So the message they are saying is simple: "be prepared, but don't panic"
