Neck straps are in common use with the bass clarinet, and saxophones for support of the instrument. However, clarinet neck straps are so uncommon that I find it difficult to find more that two or three models on the ultimate source of all knowledge (the internet).
Many people misunderstand the clarinet neck strap. I believe is is very unwise to think of it in the same way people think of the saxophone neck strap - as a support device. The clarinet will gain some support from a neck strap, but the purpose is that of a stabilization device.
The clarinet requires a great deal of side key manipulation. More so than most instruments. This can lead to a natural unbalance that can make it very easy to lose efficiency. Neck straps can limit this movement and improve stability and efficiency.
This won't necessarily be evident to beginner or intermediate players, and the neck strap may look/feel awkward to those that are not used to it, however, the gain in efficiency can be very evident to advanced players.
Ultimately, any equipment choice is a personal decision based on what works for you. I find clarinet neck straps to be a benefit, but you may not... but you probably will.
...On a final note, don't do anything with give in it (Like neotech, elastic, etc.) the totally work against the stability factor (just my opinion!).