the tensile strength of 316 stainless(a pretty standard stainless) is the same as 4130, as is it's rockwell hardness(standard hardness scale). the main difference between the 2 materials is the chromium and nickel content in stainless. it's because of the high nickel and chromium content that it has that nice colour and doesn't rust. Stainless is also about 30 + times more expensive than cro-mo and has a slightly lower yield strength(the point at which material deforms under stress or the elasticity) but it's still high enough to use.
JUST FOR REFERENCE
Cr is chromium, Mo is molybdenum, C is carbon, Mn is manganese, P is phosphorus, S is sulphur (or sulfur if your a yank), Si is silicon and Ni is nickel.
the bulk of both is Fe or iron
4130 cro-mo has in it
% Cr % Mo % C % Mn % P (max) % S (max) % Si
0.80–1.10 0.15–0.25 0.28–0.33 0.40–0.60 0.035 0.040 0.15–0.35
316(316-316L-316H as in carbon content low normal or high) stainless steel has in it
% Cr % Mo % C % Mn % P (max) % S (max) % Si %Ni
16.0-18.0 2.0-3.0 0.03-0.10 0.04-2.0 0.045 0.030 0-0.75 10.0-14.0
316L tends to be thicker stuff for welding(above 6mm)
316 is available in most pipe sizes, well we had them at the last place i worked. I had a few lengths of 22mm stashed to make some bars and seatposts from, but the place closed down.
4130 case hardens very well and easily, which is good for making a material hard but not brittle as only the outer skin of the material is hardened.
stainless 2205 is harder/stronger but you get to silly money for the materials.
i reckon the main reason would be that it's not economically viable, and resistant to stress cracking.
there are loads of different types of stainless, but the they get more expensive and harder to work with when you move away from the common 304 316 types.
examples with family/grades/advantages/limmitations
Ferritic
410S (1.4000)
430 (1.4016)
446 (1.4749)
Low cost, moderate corrosion resistance & good formability.
Nominal corrosion resistance formability, weld-ability & elevated temperature strength.
Austenitic
304 (1.4301)
316 (1.4401)
Good corrosion resistance and cryogenic toughness. Excellent formability & weldability. Widely available.
Limited resistance to stress corrosion cracking. Work hardening can limit. formability & machinability.
Duplex
2205 (1.4462)
Good mechanical strength.Very good pitting, crevice and stress corrosion cracking (scc) resistance.
Application temperature range more restricted than austenitics. More expensive, and less widely available than austenitics.
Martensitic
420 (1.4021)
431 (1.4057)
Low cost, hardenable by heat treatment with high hardness.
Limited formability & weldability.Nominal corrosion resistance.
Precipitation
17/4PH (1.4542)
Strengthenable by heat treatment hardening giving better toughness and corrosion resistance than martensitics. Weldability better than martensitics.
Restricted availability, corrosion resistance & formability.
right, that's enough boring info.
to put it in a sentance:-
too dear, too awkward.
