There are several reasons:
We do not change resolution or any other parameters of the video. We do not edit video which you download. We only provide a link to the original file which is located on Tiktok servers.
Basicly that means that we can't make better quality because the original file is in poor quality.
It costs some money to support website like this. We have to pay salary to our coders. Other expenses include servers, domain name, security protection costs, etc.
Ads are the only way of our funding, so we can't remove them. Please, treat this with understanding.