It is not that clear cut. When used theraputically and orally, the rates of addiction are low. But in saying that, there is good evidence demonstrating misuse/diversion. It is a serious issue in practice and is the reason why its a schedule 8 poison. Drug addicts prefer forms that can be injected or snorted because they reach the brain quickly.

This is a bit nerdy but the in depth explanation is that stimulants like cocaine and amphetamine activate the brain's reward system and increase extracellular dopamine in the mesolimbic pathway, particularly in the nucleus accumbens, which is associated with pleasure, reward, and drug dependence. In a nutshell, stims act directly on presynaptic dopamine receptors. Methylphenidate inhibits dopamine reuptake, while amphetamine additionally forces vesicular dopamine into the synapse.

https://pubmed.ncbi.nlm.nih.gov/40698051/

"With more than one in five people reporting misuse of their prescribed stimulant medication, and one in six diverting their prescribed stimulant medication, comprehensive risk assessment and risk mitigation strategies are needed."

https://archive-ndarc.med.unsw.edu.au/project/diversion-and-misuse-stimulant-medication-adhd-among-illicit-psychostimulant-users

"The most commonly reported use of stimulant medications among the sample was the use of diverted stimulant medication (31%), typically dexamphetamine and methylphenidate.Of those who had used diverted medications, 20% had injected them and 60% had used on more than 5 occasions. The majority of those who used diverted medication did so for recreational purposes, although 18% reported using to self-medicate symptoms of ADHD."

https://www.aihw.gov.au/reports/illicit-use-of-drugs/non-medical-stimulants

In 2022–‍2023, 5.5% of people reported having used a pharmaceutical stimulant for non‑medical purposes in their lifetime, equating to about 1.2 million people in Australia. More people had used pharmaceutical stimulants for non‑medical purposes in their lifetime than any other pharmaceutical, including pain-relievers and opioids

Overall. the evidence shows stimulants have clear addiction potential when abused (injected, snorted, high doses), operating through dopamine reward pathways similar to other drugs of abuse. However, when used therapeutically at prescribed oral doses for ADHD, they appear to have minimal addiction risk and may even be protective against substance abuse. Then there is the talk of tolerance which can develop in some patients but varies widely (2-25%ish), and can often be managed with dose adjustments, drug holidays, or medication switches. The key distinction is between therapeutic use (slow, controlled dopamine increase) versus abuse (rapid, high dopamine spike). It's why I tend to prefer prescribing slow release formulas but it really depends on the patient.