Yes, as Bitcoin is still not legal in most countries of the world so Bitcoin transactions are considered illegal. And no illegal currency ever gets much priority as an asset. Although Bitcoin is being transected in different parts of the world, it is very little compared to fiat. If governments take a positive view of Bitcoin or cryptocurrency, then surely Bitcoin will be considered more as a currency. So at present it is better to consider Bitcoin use as an investment tool rather than as a currency. It is also true that in the future Bitcoin will start to be used as a currency. As different countries are validating Bitcoin, we can say that Bitcoin will be used as a currency in the near future.
Bro what are you trying to say, the fact that Bitcoin is not legal in some countries doesn't mean it can't be described as an asset, those countries who placed a ban on Bitcoin is best known to them and if you make you research you'll see that it's mainly because their government can't control the currency that's why they placed a ban on it.
However you need to ask yourself this question (what is an asset?) Then when you've made your research to find out what it means then you should try and figure out if it falls under the category of any definition you find out about what an asset is, also I won't deny the fact that it's a currency (digital currency) one can also say it's an alternative currency for carrying out transactions but based on it's increase in value over time it's has become an asset (digital asset).
If Bitcoin can't be described as an asset do you think many investors (whales) for instance Michael Saylor who is the owner of Micro Strategy and other top institutions and Business men would buy it an hold for a long-term, infact what do people hold for a long-term if not for an asset, if bitcoin was meant for transactions alone, then there won't be any need for buying and holding for a long-term and it increase in value over time has made that possible.