Is like trying to force your car dealer to build now an airplane because your car is now 'not enough'
A roadmap is something used to communicate your vision and set targets for both internal and external stakeholders.
You need targets to achieve big things. Coaches and Athletes set targets. Entrepreneurs and startups set targets. Teachers set targets for students. If you think a coin can just exist and people will back you, think again. Using your car metaphor, if you think in the automotive industry, once a car manufacturer is able to create a car and believe that that is enough for people to continue to buy you(over the competition), think again.
Car manufacturers are constantly tweaking, upgrading, re-designing to make sure they've got all the latest gadgets and gizmos and are up to date with mechanical/safety/design and cosmetic standards. The car has been around for over 100 years and is still constantly improving. A crypto currency which has existed for 4 years cannot simply say that's enough. There are now over 800 Crypto currencies.
As the others mentioned, this coin is not dead. At around the 200 rank (market cap) this coin has relatively high daily volume (over $1m every day). The developers are also constantly working and have their minds open to future implementation of segwit(although some are reluctant)
I think most, if not all of the investors/backers would just like to know their funds are in the right place and that that place would allow for their funds to be part of a mainstream or widely used payment system.