Actually it's only fairly recent laptops which automatically or by user settings, constrain charging of the battery to nn% of full to 'preserve the battery life'.? Many out there don't.
In fact it's only my most recent, a two year old Legion 5 out of all I've used or owned (used countless in various jobs, owned about 5 ranging from a very early Zenith through an early DRC spec AMD64 HP based, through to more recently a HP quad core AMD based which I still use for radio stuff, currently a Legion 5 used predominantly not for gaming) that actually had such a feature, even the second oldest (five years old - used primarily for radio programming and data mode ops) didn't have any constraints beyond going to trickle mode charging after battery was fully charged.
Hell, even my old MacBook Pro (ten years old) didn't support it, and they were pretty much on the cutting edge at the time for battery maintenance. So it's safe to say it's only fairly recently (say within 3 years best case) in the mainstream and maybe some very high end older stuff that constrained battery charging for battery preservation.? Some ToughBook models did, and I mean older 'real' ToughBooks with the Ti construction.
I do, however, have a few external Li-Po and Li-Ion chargers designed for standalone laptop battery charging/conditioning that do support constrained 'less than full charge' maintenance charging, and those are about five years old - not intended for laptop users but for specialist test equipment that used commonly available laptop battery packs.
I've also possessed ex-professional market (IE military and suchlike) radio transceiver gear that did have such features, not for everyday use but mostly for when units were long-term stored for rapid deployment so kept on a maintenance charging setup, but could fast charge to 100% from about 60% maintenance charge very quickly.
So it's a case of some Li-Po/Li-Ion powered gear? do, some don't and sometimes non-laptops use laptop batteries which are maintenance charged with nn% constrained charging - uncommon examples include some of those professional portable ECG etc units that are essentially custom portable PC's.? Some professional test gear also uses constrained charging too, as well as a few uncommon in the West professional spec radios that used laptop battery packs (2-4x depending on their specific applied classification).
?The US spec medical portables I have picked up surplus faulty (intended to gut for parts and reuse the cases) had both constrained charging capability on the SLA and Li-Ion charge circuits - notable I sidelined those modules for reuse as combo items like that are uncommon and yet could be incredibly useful for portable radio power assemblies.? But given the units had defib functions, hardly surprising they are dual powered with auto changeover handling.
