Asserting that a fundamental plot is essential is a lie, Bengt. Fundamental plots are not essential as a generality. Just look at the number of people flocking to drop-in/drop-out gaming at stores. Many aren't even playing linked adventures. Each player's character is its own continuity... which sometimes overlaps with others' continuities. Plots are great when everyone has buy-in on them... but a GM with a plot the players care nothing about is just about the single worst thing I've experienced in 39 years of GMing and playing... because it often leads to frustration of players, GM, or both. And GM frustration all too often leads to railroading and/or punitive encounters for picking the wrong path.
Humans are pattern finding machines. So much so, that there are words for when we assert pattern to random noise, or associat two genuine patterns that are unrelated (or distantly cadet on the same source, such as total Power use in the US and thefts of cars in the US... neither is causal to the other, nor even directly correlated... but both are functions of increasing . (pareidolia, apophenia, spurious correlation). When confronted with semirandom mission data, unless they see the rolls, players are likely to ascribe patterns that are simply due to the framework and the dice. And that's a very useful tool for GMing. Especially for newer GM's... if you can hide the rolls in between session play, they may never even suspect they're random. And in a well crafted random tableset, patterns are inevitable by design.
I'm not saying natural consequences of their actions shouldn't be added, either... adding upm the natural consequences makes the difference between strictly episodic and continuity-maintaining campaigns... but that need not be part of the initial framework, at least, nothing past the initial hooks the players give. And even then, those are merely two points on the spectrum. If they blow a mission, next time that supplier is rolled, maybe roll an extra die on the random component, and drop the highest die. If they've done a bunch of work for one employer, maybe roll an extra and drop the low one. This develops natural antipathies to and from various employers entirely without direct GM driven antipathies.