That's not so - there are several software settings which can drastically affect your download speed e.g. the mtu setting, etc.
The easiest way for someone who doesn't want to go through a learning curve on how to tweak the settings for best effect [and the settings will differ a lot between different setups] is to use something like TuneUp which leads you through the process step by step.
If you consider the number of variables in use on different computers it stands to reason that no one setting will suit them all! Even just switching from ethernet to wifi would need a software tweak to get the best out of it.
If you want to check your dl speed use DU Meter [most isp's know and respect it].
Also don't forget that your speed will be governed by the slowest link! If you want to get the best speed get onto usenet and you will max out your connection every time up to the limit set by your usenet/is provider.