Used to indicate that, given the circumstances, it is sensible or reasonable to do something because there is no better alternative.
Used to suggest doing something because the likely outcome does not differ substantially from other options.
2.
UKUSGlobalinformalcolloquial
Used to introduce a frank or candid statement that the speaker believes should be said now; roughly equivalent to 'I might as well say' or 'I ought to mention'.
3.
UKUSGlobalinformal
Used to express resignation or acceptance toward an undesirable but inevitable action.