In a few lines...
I don;t like the view that 'higgs boson transmits the higgs field'... I find it unnecessarily confusing.
Now to your main point; the Higgs Boson does not decay only in photons or 4 leptons...
the Higgs boson by theory couples to all the fermions through Yukawa terms in the Lagrangian and to gauge bosons (like WW or ZZ). So it couples to quarks, leptons and gauge bosons... the quarks and gluons are important because that's how the Higgs boson is produced in the first place [when the protons collide]... It then can decay to several channels... it was the photon channel and the ZZ (that results to 4 leptons] that was first observed because if I recall well they give the clearest signal...
To what the Higgs Boson prefers to couple to depends on its mass, see eg Fig 11.4 here:
https://pdg.web.cern.ch/pdg/2015/reviews/rpp2015-rev-higgs-boson.pdf
with b\bar{b} being the dominant decay products of the Higgs...However most of the decays to "QCD" objects (like quarks or gluons or taus), that are seen by the detector as "jets", have a very strong QCD background. I believe eversince the Higgs was discovered more channels were used/observed... one I am sure about is the \tau^+\tau^-.
Now if your question is why it couples to all these; well you need to take some Particle Physics course... the main idea is that everything couples to everything as long as a symmetry permits it, and if it doesn't then you have to find a good reason why not.