Well, just remember - just as Styles are made at least in part so you can notice that the scruffy assassin is using Fire Dragon Style and wonder how they know it [1], spells cast through a Lineage are incredibly distinctive. Anyone educated in the characteristic styles of various schools will be able to look at your characteristic Heptagram style and pinpoint it - and might even be able to tell who you learned it from, with a good roll.
Making a new Lineage means starting from scratch, shunning your old teachers, and casting off your old methods. And Lineages might be slightly easier to increase than Breeding, but they're really, really non-trivial. A new sorcerous school starts off weak, and takes a very long time to build up the required metaphysical weight.
That may sound unfair, but that's a hard consequence of the fact that the mechanics and themes of this sorcery rewrite is there to make sure that Sorcery Is Privilege. Hence, start-up schools are weak and lacking compared to the institutional behemoth of the Heptagram, which has "literally thousands of sorcerers have learned here over the centuries and we learn techniques taught to us secretly by Sidereals so we also invoke the power of Heaven in our spells".
Keris can't get any Lineage, because she uses her own personal bastardised part-Salinian-part-Hellish-Kimberyian casting style. She has no disciples and basically made up her techniques as she went. To even get to Lineage 1, she'd need a notable number of people to be taught and follow in her style - and that's not easy, because there aren't exactly a large number of sorcerers in Creation. Building a new school of sorcerers is a long term investment which means you'll probably need Dragonblooded disciples or to put a lot of effort in getting mortals up to Enlightenment 3 so they can learn your techniques.
[1] They're probably a Sidereal.
Okay, at this point I've twigged on an odd connection and I have to ask something about raising lineage after the fact, and how far it can go.
I'm reading that one can set up their own school to increase their personal lineage, and it likewise seems reasonable that one could increase the potency of the Heptagram's Lineage by expanding the size and prestige of the school, as well as just ensuring its continued survival.
Thus, at the very farthest end, is invoking science
as an institution --- with the constant, mass scale exchange of knowledge among a vast field of practitioners --- a, heh,
theoretically possible means for someone who wants a supremely potent Lineage? (Nevermind for the moment the logistics of
acquiring that many millions of sorcerers, nor of herding that many cats.)
Conversely, realizing that a tradition of ten million sorcerers is also a tradition of ten million
competitors --- all of whom can likely sustain at least one single, potent spell capable of ruining each other and all of whom can make just as much use of those manses, artifacts, elementals, followers, demons princes, and cults as you can --- would one be able to incite infighting, sabotage, and other backstabbing among members to reduce the potency of a lineage?
(I get the picture of the sorcerer and school-founder burning all his works, not out of some secret threat to the world forseen in the depths of knowledge, but because the mad old god-kings realized they had created something that could one day stand beside them in power, and realized that they wanted to stand
above others much more than they wanted to simply stand tall. Personal power thus coming into conflict with common wealth.)