I think it's because of the price. OLED is priced waaay out of reach of most consumers.
Plus the fact that despite the high price, LG and Samsung are losing money on OLED TV sales. Manufacturing cost is still very high at this point (partly because of BOM, and partly because of low yields). The makers won't push a product that they don't make money from. The high initial investment and development costs are apparently what stopped Panasonic and Sony from dipping their hands into an OLED joint venture.
If their fabs progress as expected, LG is projecting that they can start to break even on this product by the latter part of this year (I doubt Samsung would be behind on this). LG and Samsung are in such tough competition to get this product to the market that they are suspecting that corporate espionage is happening. Once the tech becomes truly profitable, the panel makers will surely ramp production and start pushing them to the shelves. Once they reach this point, they will start milking the technology with sustained premium pricing to pay for the original investment until other producers get the capability to deliver competing products.
Right now the 4 big panel makers are:
1. LG Display (Korea)
2. Samsung (Korea)
3. Innolux Corp. (Taiwan) - formerly ChiMei
4. AU Optronics (Taiwan) - formerly Acer Display
Most TV makers just source from these 4 panel makers. The largest Japanese panel maker (Sharp) is now a small niche player when compared to the market shares of the top 4.
The Taiwanese panel makers (Innolux and AUO) are closing the gap in terms of LCD performance, but they they may take some time to bring the fight to OLED (based on the time they took to develop their LCD tech).