I think it is an important and requires more than a glib answer, BUT practically speaking it depends
Counter intuitively it may well be that the bigger the aircraft the more likely it is you won’t always have an alternate - or a real one at least. The reason I say this is for example the A380 (and to a lesser extent the 747 and 777) is not going to fit into every airport so the potential alternates become few and far between in some cases and the fuel required to carry an alternate is higher.
I note you are in Australia, so the lack of suitable airports drives a lot of decisions, whereas if you were operating in the US or Europe the decision making is different.
Perth for example is so far from anywhere useful that many carriers use “island reserve” or a version thereof.
in the machine I fly we carry technical alternates where we can and real alternates when necessary, and the times you need a real alternate it has a real fuel impost, though we can, under certain circumstances give the alternate away.
so to answer your question, a blanket, always carry an alternate answer isn’t necessarily the best or only answer