Ukraine is a very corrupt country. Exemption from cryptographic taxes can give freedom to laundering dirty money to members of parliament and the government.
Most of the third world nations are extremely corrupt, and the former-USSR nations such as Ukraine are not an exception. That said, I don't think that BTC is a preferred method to pay bribes to the politicians. They don't need to pay bribes in the form of crypto, when it can be easily done in the form of fiat cash (either in the physical form or the digital form). The only concern here should be the exchange rate of the national currency (Ukrainian Hryvnia), which has lost almost 70% of its value during the last 5 years.