What is the use of signing a contract?
Can the client sue me for poor quality work if we don't have a signed contract? (Emails are the only sources of proofs for invoices and payments)
With or without a contract, there are always many ways, for two sides, to sue each other. You get your work done bad, the client gets it proven that it's certainly your work, then his loss is considered to be reimbursed by one who caused it (you), and there's no need to have a physical paper that states your relationships. But having a contract may accelerate things. It may turn out good or bad for you, equiprobably.
But there are a lot of positive points about having a contract signed. It disciplines both of you and sets boundaries. It makes it clear what a contractor should do to state his work 100% complete, without scope creep, unending additional little features, and all that hardly anticipated stuff.
A contract fixed a "project triangle", which consists of cost, time, and budget. You and your client agree, once and forever, that this project will contain certain set of features and will cost a client certain sum. If you are in doubt about whether such boundaries are useful then, well, you probably haven't finished a single freelance project yet.
Having a contract signed is also a good way to strengthen your
bureaucracy formal relationships skill. You'll have probably been glad for such an experience after being offered to dive into a really big and profitable gig.
There is no guarantee with or without a contract that you will not have legal action taken by a client. The contract would/should state the work that would be done and the payment for that work. In the case of a law suit, there would not be a case of he said, she said when there is a contract in place. This can be either positive for you or negative depending on the circumstances and the evidence of the claims being made.
It depends on you. If you sign a contract with remote client, who says that you cannot tell him your name is John Smith. If you mess up, he can sue John Smith.
In freelancing, it's all about trust and building a connection. So if you do a good job, the client will recommend you by your name to someone else. The same is if you do the bad job.
Also, the contract is not a Bible. You can choose what to put in it. If you don't feel like putting your real address, then don't do it.
I see no reason why should you avoid contract taking into account that you are skillful and you can complete the job given and your intentions are not to trick the client.
If you deliver work, it has to be "state of the art" or "lege artis" how the doctors call it. There is a certain amount of quality expected, which is usual in your business.
You can of course deliver lower quality if the client asks you for it, but then I would always get it in writing. To avoid later confusion, you should put all agreements in writing anyway, be that a contract of emails.
The next point to think of is if something goes wrong, you can get sued by the insurance company of your client, not only by the client. So even if they don't want to take legal action, they have to. Same if it is a company with stakeholders. Or if the client goes bankrupt, someone will pick up all the pieces and one of them will be you.
Make contracts, it can save your life!