The free version is too limited , impossible for me to do anything with. why shouldn't the whole program be free except exporting functions?
On this subject are a few answers one of them would be the business aspect which Tom explained, in order for scirra and the developers of Construct to keep improving and developing the product they need revenue.
Offering the program for free wouldn't allow them to do that, so the freemium model they chosen is limited.
Now you said why isn't only limited to the exporting functions, well that is because if scirra would allow you to make a full game with a forced splash and give you access to html5 export option only.
You would be able to turn that html5 export and convert it using other services or a custom interpreter that would allow that html5 export to run on android, ios, windows, linux and other platforms, that's why the limitations.
Construct as any other software is made out of code, code that can be reversed engineered if put enough time in can be exploited to the point of rendering the scirra business model to nothing more than a freemium product in the case they would give access to all the features of the software on a free version.
A good example here is all the games like (Ghost Warrior Sniper and others) that offered a demo fully packed with the entire code of the product, but was locked so you can only play a surtain amount of the game that would make you buy the rest, problem is having the entire product locked but all the features built in the demo like that, people were able to crack it and therefore you have the torrents all over the internet allowing you to download a free pirated copy illegally, which in terms the business creating the game, loses money that instead of going to their development and improvement of the game are basically wasted, or not spent at all.
Having Construct on a cloud system locked is the best choice as the content is not fully on the client side. It can still be cracked (the saved version on the client's browser most surely to hard to be worth it), however no longer getting any updates. But cracking a cloud based software would take to much time and effort and would be for nothing as in the time pirating a software like this, the original creator would be making tons of other updates where you only will get a old dusty version while free useless in the end, as the internet technology constantly evolves and changes everyday.
I hope you see the problem here and how the limited features the free version has, are best fitted to the current situation.
However if you want to learn something more than the basic functions, there are tons of schools all around the world using Construct as their programming software teaching tool.
You can join one of the classes that would allow you to practice to the extent you want without limitations.
And when you would be ready to publish you can then buy a full license of Construct and publish your game.
I might over done the information needed, been carrying myself probably to much in depth, but that's some of my logical speculations why the limitations of Construct exist.