Sometimes you think you can't because you either haven't learned the right tricks, or because it takes more effort and thus you opt to fork off your work in a separate long standing branch in order to optimize your development velocity at the expense of possible surprising costs during merge (if other people also make your same choice).

Other times it's genuinely necessary to make a long standing branch. In those cases, you just do it. Trunk based development should not be a dogma, just a different default choice.