A design of Tom's from the early-mid 1980s that had load lifters: the Wild Limpet. In use, Tom found that the load lifters didn't do much for this pack (except distorting the shape of it) because it didn't have a frame.
Load lifters are somewhat ubiquitous on large internal frame and external frame packs and, on those packs, can be useful; their application or utility on smaller packs is, in our opinion, of dubious merit.
From a guide to backpacks:
“Load Lifters - Part of the shoulder strap and is used to lift the pack's weight off the shoulders.”
There’s something akin to a “sky hook” in this concept of how load lifter straps function: how, exactly, does the load get “lifted”? Where’s that weight going? Who, if not the wearer, is lifting this weight? Who, if not the doer, is performing the action? Does free will exist? We digress.
With a large capacity external or internal frame pack, there can be some advantage gained by cinching the top of the load closer in, towards the user’s shoulders, and thus closer to your center of gravity, and some folks swear by load lifters on the big packs they carry.
With an entirely frameless pack, there’s nothing rigid for the top end of the “load lifter” to pull against, and when you tighten these straps you end up simply distorting the soft, unstructured top portion of the pack, distending it over your shoulders to no avail. That applies to packs like the Synik, Guide's Pack, and Synapse as well, where the internal frame ends roughly where the padded shoulder straps attach and does not continue any higher up (as a frame/frame sheet typically would in a larger pack intended primarily for extended backcountry use).
Our backpacks have a shorter internal frame because they're fairly small daypacks: if we added “load lifter” straps to our daypacks, they wouldn’t really help “lift” any weight – it'd just distort the soft top of the pack and would do little or nothing to keep the pack’s weight closer to your center of gravity. On the other hand, if we made the internal frames used with our packs longer (taller), extending it higher than the top of the shoulder strap attachment point, it would, in our opinion, start it down a path of becoming a backpacking pack, rather than the travel, EDC, and day-hiking packs we intend them to be.
We're open to your experiences, thoughts, and feedback; post here in the comments or send a note to firstname.lastname@example.org