Well it all comes down to money, research money. In Australia about 1/12 of the grants to the NH&MRC (the medical research funding body) was funded in 2015. It is expected go to 1/8 this year.
To get funding the topic has to be important, the team excellent, the track record excellent and the outcome of the research will benefit people either directly or fundamentally.
The 'best' figures for the size of the trans community in Australia and NZ is between 3-4%. A significant number as far as a needy population is concerned. But the community has not made the argument that better treatment is required. Unlike say breast cancer, heart disease etc. So the focus of the funding body does not see the issue.
The other problem is that treatment options for trans people in Australia and in many countries is outside of the national health insurance areas. So for example if you have breast cancer in Australia all of your treatment is free, covered by the national health insurance. Saving the country money by creating better health care options is seen to be financially important.
Since the trans community basically has to pay for treatment themselves the government doesn't see it as a saving.
Our best bet for research funding is from the USA military. Believe it or not! As they are not happy with treating soldiers who have suffered genital mutilation from warfare they are keen to find ways of solving that. Such therapy will then go into main stream medicine and hopefully help all.