Why don't automakers commonly make 3 or 5 cylinders?

Most reliable cars like toyota or honda are only come with 4 and 6 cylinder are available and what do you think of those engines?

There's still exist, like discontinued inline 5 of vw, few inline 3 on ford and mitsubishi but 3 are unreliable.

The engines spin at a very fast rate, and an odd number of cylinders will cause an imbalance, which will cause vibrations. There have been a couple of attempts using a 'balance shaft' that spins along with the crankshaft, but the extra mechanics eat-up the gains from the smaller engine size.

Inline 6 and 8 cylinder, 90 degree V-8s & 16s, 60 degree V-6 & 12s are naturally balanced, ie can be designed that the internal moving masses are always in balance.

The more cylinders, the more power strokes/impulses per revolution which makes them inherently smoother than fewer cylinders (unfortunately, they have more internal friction for their displacement than engines with fewer cylinders of the same displacement).

Advancements in design have made 4 cylinder inline engines acceptably smooth but they are prone to resonance.

There have been a number of modern inline 5 cylinder engines (Volvo, M-B, VW Group, SAAB among them) - they were really designed for engine compartments that didn't have room for a straight-6… And usually replaced by V-6s as those became available.

There have been 1, 2, 3 cylinder engines - none very successful because of noise, vibration, rough running. (even most 3 cylinder motorcycles were duds).

Some make 3's or 5's.

Any odd # or multiple of 3 causes imbalance. That is fixed with counterweights or a balance shaft, that eats up power.

So, why not just add a cylinder, that adds power And cures the imbalance?

Many take their Suzuki Sprints and remove balance shaft, have crank professionally balanced and put in lightened harmonic balancer and flywheel, and, GO! They are a light little engine, with these mods they put out a LOT for their size. But, this is a lot of work.

Some tractors…3 cylinder. Some older diesel Mercedes… 5 cylinder. It all about the need.

There are more 3 cylinders around now then ever before. Ford has their 1.0L Ecoboost in the Focus, Fiesta (Europe only) and Ecosport, The new Minis can be had with a 3 cylinder, and there probably about half a dozen others if you count Euro-only models. You're going to see more turbo 3's going forward.

The five cylinder is a rarity these days, in the US market only Audi makes one for the TT RS, and Ford makes diesel 5 cylinder, but that's about all I can think of off the top of my head. I suspect that with the turbo 4's making enough power for most people, and getting better fuel economy and lower emissions while doing so, there's not much need a for 5 cylinder these days, it's niche engine design.

It's easier to balance an inline 4 or 6.