But your internet shouldn't.
HFC is the technology predominantly used by NBN to connect Australians to the internet in metro areas. It's exactly the same infastructure used by Telstra Cable and Foxtel. Bought by NBN from Telstra for $11 billion and Optus for $800 million and used instead of replacing this aging and rusting infastructure with Fibre to the Premise (FFTP) like the government initially promised. HFC is an outdated and failing cable infastructure. Foxtel customers are being moved from the HFC network they sold to NBN to satellite because it's more reliable than HFC.
Because NBN HFC is sharing the same HFC network with Telstra Cable and Foxtel, it's forced to use less optimal and noisy frequencies that are more prone to connection disruptions. So if you're still with Telstra Cable - don't move until you have to! In addition to being more reliable, Telstra Cable customers report a drop off in speed from 115mbps to 90mbps when they move to NBN. When the Telstra Cable/Foxtel/NBN coexistence period ends, with any luck speeds and reliability will get better.
Unfortunately for now though, HFC stands for "Hardly Fucking Connected" not "Hybrid Fibre Coaxial" like NBN would like to have you believe.
NBN are focused on building new infastructure, not maintaining their existing HFC network. Unfortunately the biggest disadvantage to HFC over Fibre is it requires a lot more maintenance. For example, the f-connectors are very prone to rusting and need to be replaced every couple of years - not to mention all the many other components of a HFC network that need to be taken care of. This has been an overall terrible experience for customers - many of whom are getting constant drop outs - but don't know who to contact about it. Thankfully there's an excellent NBN complaint guide on whirlpool - but it seems insane that customers should have to go to this much effort every time there's a problem with their NBN connection!
Your NBN cable modem (Arris CM8200) is connected to a CMTS (Cable Modem Termination System) which keeps a log of every connection disruption. However it's clear NBN aren't monitoring these logs. You shouldn't have to do this, but you can monitor the logs from your cable modem and keep a log of all the drop outs you're experiencing - for more information, see the hfcmon tool for example.
Instead of NBN already knowing there's a problem, the customer is forced to complain to their RSP (Retail Service Provider) who in the majority of cases doesn't escalate the issue to NBN. Even if the issue is escalated to NBN, the best NBN will do is send out a sub-contractor from a company like Service Stream - who are only trained and authorised to fix tap down issues (issues from the power pole/pit outside your house to the cable modem inside your house). Very rarely this sub-contractor is able to fix your issue. However for most, NBN will keep sending out sub-contractor after sub-contractor who can't actually fix your issue. Ironically if NBN just checked the damn CMTS's logs there wouldn't be a need for any of this.
My wife and I use the hfcmon tool mentioned above to beep when our internet goes up/down. It's really a sad reflection of how bad our internet is that we check whether our internet is up/down before clicking links. NBN sub-contractors keep visiting, performing the same line tests and concluding nothing is wrong - why would anyone stay with NBN when they have such bad service! We're thinking of changing to Optus 5G Broadband - it's cheaper and faster. Alternatively, I'd sign up to a Fibre-To-The-Premises (FTTP) company like DGTek instantly if they moved into our area.
Having issues with your NBN HFC connection? Here's lots of technical information that might help you. Unfortunately though you're probably going to have to complain to your RSP (Retail Service Provider) and get them to contact NBN. If nothing gets done, as per the NBN complaint guide, register a complaint with the TIO and notify your RSP of the TIO reference number. Good luck!