One of the core benefits of owning a smartphone is the simplicity of access to basically everything you need a PC for. The fact that it is a mini computer and does almost every single thing your large sized PCs would do makes it a more attractive option for every human on the planet than a PC.
The smartphones played a huge role in the mass adoption of cryptocurrencies firstly because the offered a quick, swift and detailed info on what cryptocurrencies were and you could basically carry out your research and find out what crypto was from the most uncomfortable positions in the most unconvenient places its that easy unlike if we were left with just the options of a PC about 15-20 years ago.
Crypto wallets have been simplified and made easy to access and use, that even a 2 year old can understand how it works. I've never checked my crypto portfolio on a laptop but I do understand this was the case in the early days of cryptos when there were no crypto wallets in form of apps for smartphones. Smartphones also make transactions on crypto wallets easier because of how portable and easy to access smartphones are in contrast to PCs.
Mining of cryptos, particularly Bitcoin, were carried out in large machines and consumed massive space, energy and required alot of work. This is still happens till the day but has reduced drastically as the people can earn mine/ earn more cryptos with just their smartphones. This is quite a significant difference and would go down as one of the major advancements in the crypto world.
The timing of the existence of cryptos is just perfect, just when the tech to boost its mass adoption was available. The adoption of cryptos would probably have taken way longer if we were in the era of Nokia 3310 or in general, phones with poor internet access and that weren't as smart.