Those older SSL and TLS versions are insecure now or at least deemed a bad idea from today's security ideas. TLS 1.3 partly was about removing insecure modes from TLS 1.2. If HTTP/3.0 supported anything other than TLS 1.3, then those insecure setups would persist.
Of course there are disadvantages, like when you are in a lan or such. But I think those cases are covered well by the HTTP/1.x family already and if not you can always add root certificates yourself or make public DNS names you control point to your 192.168.... address.
Of course there are disadvantages, like when you are in a lan or such. But I think those cases are covered well by the HTTP/1.x family already and if not you can always add root certificates yourself or make public DNS names you control point to your 192.168.... address.