A human being daily needs something like 2000 kcal food-sourced energy, a slate of vital nutrients, 250 square feet of personal living space, some average BTUs of heating/cooling, a gallon of clean water, and a share of infrastructure to produce/acquire/deliver this. (YMMV; point of context made; details left as exercise for reader.) We can view this baseline as the objective essence of "value": one needs the aggregate of these points to sustain life for one day, anything less begins the descent into death. We can also view anything substantially beyond standard deviations of this as unnecessary (albeit desirable). SOMEBODY has to produce this, be it basic sustenance farming or creation & maintenance of high-tech high-productivity machinery; this work is necessary.

The objective value of this baseline is the true "poverty line": if you try to exist on less than this, you're gonna die; if you can acquire substantially more than this, you can start indulging in relative luxuries. For sake of simple argument (detailed accuracy left to reader), we'll use the official USA poverty line as the currency equivalent of this objective value of what it takes to keep a median human alive under normal conditions: about US$30 per day.

So...to keep one person alive & stable one day requires $30/day of work. This is invariant. If someone's work produces $30 of value (exchangeably equivalent to those enumerated basic daily needs), one person maintains sustainable life another day; if the worker "gives" that to someone else, keeping none for himself, he is literally giving his life to the other. If his work produces $60 of value, he can sustain himself for two days (work one, idle the second), sustain himself for one day and spend the remainder on comforts & luxuries, or give $30 to another and keep both sustained for a day. Technology makes it easier for one to earn more with the same expenditure of effort.

The consternation about "is work necessary?" stems from who gets to decide how the extra earnings are distributed.

If you retain your extra earnings, you are saving for future idleness (vacation, retirement) or statistical fluctuations (temporary increased cost of acquiring necessities).

If you spend your extra earnings on comforts & luxuries, you are giving others the opportunity to work for their daily basic needs thru means other than direct acquisition (building cars, writing software, acting theatrically, etc. instead of sustenance farming, hewing trees, carrying water, etc).

If you give away your extra earnings strictly voluntarily (no coercion), you are charitable (sacrificing idleness, preparedness, or comfort/luxuries for others).

If you give away your extra earnings under coercion (if you don't consent it will be taken from you, or worse), someone else is making the decision for you regarding how your extra earnings should be distributed - and this, quite understandably, produces enormous consternation.

(If your baseline earnings (the $30/day) are taken under coercion, your continued existence is threatened and the issue becomes a matter of self-defense - a separate topic to discuss.)

Is work necessary? Yes, insofar as someone has to expend effort which can be converted into providence of basic needs. If someone can work earning $300/day, then he can take the next nine days off, purchase comforts/luxuries which pay enough to sustain nine other people another day, or sustain nine other people another day without obligating the benefit of creating comforts/luxuries. This thread addresses this last point: given no obligation to produce something exchangeable for basic needs, will a populace on the whole produce more* value or less? and does the populace at large have the "right" to compel individuals to give up their extra earnings without compensation, or does the individual have an absolute "right" to keep his earnings and distribute them as he sees fit?