Do Your Tires' Speed Ratings Matter?

Along with the usual tire specs (width, aspect ratio, rim size - e.g. 205/55R16), our tires also come with load and speed ratings. For my case, it's 91V, meaning each tire could handle 615 kg of load at a speed of 240 KPH.

Other common speed ratings for cars today:

S - 180 KPH (e.g. Mitsubishi Strada GLS Sport V)
T - 190 KPH (e.g. Honda City 1.3S, Hyundai Accent 1.4)
H - 210 KPH (e.g. Ford Explorer LT)
V - 240 KPH (e.g. Toyota Corolla Altis 1.6V/2.0V)

My question is, does it really matter? I ask because there are quite a number of people claiming really high speeds (some with videos and pictures to confirm) with their vehicles, even exceeding the tires' speed rating.

Does it really pose an increased level of danger if you go 10-20 KPH above what your tires are rated at?
Likewise, if your tires are rated at 240 KPH, does it mean that it's relatively safe to go at, say, 210 KPH?

Maximum load, at maximum speed, with the tire not fully inflated to cope with the maximum load (say... just 28-32 psi, when high load rating is around 40 psi) can lead to a blow-out. But it takes a while. The NHTSA test for this is running for dozens of hours at just over full load, I think.

So, yes, if you drive at very high speeds for long periods of time, it matters.

If you're not an absolute dip**** and drive at sane speeds on tires that are not designed for high speeds... then it's not such a big deal. A tire will not fail right away if you pass its speed rating...

But if you consistently drive the tire over the speed rating, you increase the chances of failure significantly, especially if you don't inflate the tires properly.

It does concerns me.

The higher the ratings the better, its means "higher safety level" also.

Same rating & the same uses, it compromises " safety factor".