You will see some people here at bitcointalk.org who loudly claim "All altcoins are a scam!"
People do discourage altcoins always because of the risk involved in it, I haven’t seen anyone saying all altcoins are scam, but no altcoin can be reliable, any altcoin can fail us at any moment, that’s why people are being discouraged from investing in altcoins, and bitcoin is the only coin which I know won’t fail us.
We have some altcoins that have been in the market for years, and they are really performing well, I don’t think anyone will call them scam because they haven’t scammed anyone in any way, but they are not reliable, anything can happen to those coins in the future, that’s why people are not encouraged to hold them.
If you check the coins entering the market right now, and how they are performing, then you will know why people are tagging new projects as scam projects, it’s even difficult to identify the real ones now because the scam ones are just too much.