I'm an amateur author writing my first webnovel on this site and can share some of what I've noticed.
1) When creating a brand new novel completely from scratch, it is nearly impossible to keep up with novels that are already very far along especially the professional ones with a stockpile of chapters being translated.
2) Personal life gets in the way. We can't always spend the entire day typing out our chapters.
3) Some of us new authors live paycheck to paycheck and have to work a large part of the time and thus have very limited free time. Add in a personal life and we have even less time to churn out new chapters.
4) Webnovels tend to be judged on their release rates and chapter counts. For new authors to be able to compete with established novels we often have to make shorter chapters to up our numbers and release rates. This may also lower the quality of our work.
5) Many of us authors don't have the energy to keep going at our fastest release rate. Our motivation also takes a hit when nobody comments or we only get negative comments. I personally see the number of collections my book is added into fluctuate seemingly without reason. I try not to take it personally when my numbers go down but I'm not even given a reason why from those that drop my book. As far as I know, it costs nothing to keep books in your library, so why drop any? Authors can see when their book is dropped and this hurts our motivation big time.
6) We work hard to make an intelligent original work only to see Fanfiction and works of less quality skyrocket in popularity while our reader numbers crawl along. This could be included in loss of motivation but it also makes us step back and rethink our reasons for creating our stories. This leads to #7
7) Sometimes authors get stressed out by the pressure and lack of reader response. To destress we may take time away from creating chapters to re-motivate ourselves and reenergize to come back fresh and capable of typing out quality content again.
8) Very few of us original authors are actually getting paid for the effort we put in. We are doing this for free most of the time. Ask yourself, would you do all that work for free month after month? If you said yes, would you REALLY put up with criticism and the constant pressure to release more chapters day after day spanning many months just trying to be noticed, ALL for free? Unless you are very passionate and care about your work or just really like that kind of pain, I doubt you'd put out more than one hundred chapters of quality content of at least 2k word length each within a year.
There are insights and explanations I haven't included and I can't speak for everyone but at the very least I hope I've explained some of what goes on for us Original authors.
If you've actually read this far, I salute you and hope you understand at least some the plight of me and my fellow Original authors.