Have you tried it recently? They changed to a new captcha not so long ago, after which the transaction accelerator was available most of the hour. It used to tell me I beat 95% of the users with the captcha. Now, it tells me I beat 8% of the captcha, and the accelerator is instantly unavailable. So I can only conclude bots fill it up. Maybe someone created a paid service that relies on ViaBTC.
If I'm not mistaken, the Chaptcha model replacement occurred several weeks ago or last month. I also regularly use ViaBTC to accelerate my transactions. Of course, I did this after the fees really went crazy due to the ordinal hype.
ViaBTC provides 100 transactions that can be accelerated for free every hour. And in the last month, every 1 hour there were actually lots of free transactions left. But in the last 2 weeks I also felt surprised. In fact, I also have the same thoughts as you. That there are those who take excessive advantage of this. using bots or whatever I don't know yet.
But I researched it and usually ViaBTC will immediately automatically provide 100 free transaction accelerations every time the hour is even. like 00.00, 01.00, 02.00 like that every hour. and I was really surprised because in just 1 minute the 100 free transactions would always run out and this had happened in the past few weeks. In fact, in just 30 seconds, I once checked, for example at 00.00.30, it turned out that there were only around 11 more free transactions left. and at that time I was almost late in entering my transaction. luckily it worked. Because every time I make a small transaction, I will do it, for example, at around 00.58. and then I copy the tx hash of my transaction and then paste it on ViaBTC at exactly 01.00. and it will work. because if I'm just 1 minute late then I won't get the free transaction because the 100 free transactions will have been used up in approximately 1 minute.
But there are certain hours when there will usually still be plenty left. So in 24 hours it's not always like that. Like I once checked at 01.30 UTC and there were still around 20 left. But in the next hour it turns out that this doesn't happen anymore, aka the transaction will quickly run out again in approximately 1 minute.