Why reactive components have less influence at low frequencies?
For both capacitors and inductors, their impedance varies with increasing frequency. Inductor impedance increases with frequency, while capacitor impedance decreases with frequency.
That is:

Inductive Reactance: \$ X(l) = 2\pi F L\$
Capactive Reactance: \$ X(c) = \frac {1} {2\pi F C}\$

In system design, parasitic (unwanted) inductance shows up in point-to-point series connections, blocking high-frequency current in them. Parasitic capacitance shows up as shunt coupling between signal connections, with that coupling increasing with frequency.
Stated another way, wires behave less and less like pure connections with increasing frequency because of these \$L\$ and \$C\$ parasitics.
This has influence on high-performance board design. These days, CPU boards tend to use fat power traces or even entire planes devoted to ground and power to minimize inductance. Likewise, capacitance is managed by separating signals from each other, and with controlled impedance layout.
The parasitics can be useful too: power and ground planes are often placed next to each other to improve power noise bypassing through inter-plane capacitance. Controlled impedance transmission lines can be fashioned right on the board using carefully-specified traces and reference plane distances.